You said "conflict they intend to instigate", sorry if I misinterpreted that but it sounded like you were talking about a hot war

That's why I can't put total stock in this narrative of hope and locked-in, in-escapable demise for the worst empire the world

But again, this is not the narrative I, or others, are necessarily pushing. My view is that the US as a global hegemon is on its way out - but as a regional hegemon, in the Americas, it probably still has a lot of juice left. I've made the argument before that US withdrawal from the periphery will lead to a reasserting of authority in its immediate vicinity (so, bad news for Cuba, unfortunately...). They're going to be causing trouble for decades more - but there isn't going to be another Gulf War, they just don't have the capacity to deploy that many assets anymore.

most of its enemies are incompetents not run by scientific socialists who I believe have that power incompetents do to snatch defeat from the jaws of victory

And is the empire not full of incompetents too? This seems to be a pattern that keeps popping up, the assumption that since the US is the global hegemon that must mean they're totally competent and secretly running a 5D chess game behind the scenes, despite all evidence to the contrary. The US keeps making profoundly stupid decisions. If we're going to consider the scenario of anti-imperialist countries fucking up, why wouldn't we consider the scenario of the US, say, getting involved in a stupid pointless war, burning all its munitions, and collapsing its economy? Why would the first one of these be valid and the second one not? What evidence do we have to go on for the US being so competent? Now, certainly, we shouldn't rely on the them being dumb, but we also shouldn't just assume all these other countries are stupid, that does a great disservice to the people actually in active struggle against the empire. Saying "most of its enemies are incompetents" I feel is a deeply unfair statement, certainly there are critiques to be made, but "incompetents"? Come on.

that has shown a dramatic ability to reshape the world and move mountains and repeatedly do the impossible due to its size

Has it shown that ability? This is a wild overestimation of the US - they became the hegemon because the other prospective hegemons beat the shit out of each other in two world wars, and they had a continent with a ton of resources. What amazing feats has the US actually pulled off, that put it so far above other empires? If anything, the Brits should get this kind of credit, given the scale of their conquests from the starting point of the British Isles. And, well, their empire eventually decayed just as well.

In fact, this situation is precisely an argument for why the US might not make it out of this just fine. They've had one of the most spoiled existences as an empire, they never had a Cannae moment of an enemy at the gates with most of their army slaughtered (the Burning of Washington maybe sort of counts, but in terms of actual military casualties it's nowhere close) , they've always had oceans protecting them from interference by other prospective empires, they've had a great wealth of natural resources, all of this is evidence for the empire not being built to withstand actual great adversity.

too much based off of unreliable "analysis" channels without access to real detailed information

Okay, but what sources are your analyses based on?

control of global shipping straits

The US doesn't fully control shipping straits though, that's the point I'm making! The US of the Cold War may have - but the one of today is struggling with readiness issues on its ships and pathetically slow construction of new ones. Their navy is still ahead of everyone else's, but being №1 doesn't directly translate to actually being able to control the entire ocean. They literally had all of their active carriers occupied by Iran until recently! How do you see them controlling several chokepoints all at once given their current performance?

land air and naval bases

Which have just been demonstrated to be highly vulnerable?

China can devastate US presence in the SCS and push them out but they don't have force projection to push them out of Diego Garcia or Somaliland or Greenland or the Panama Canal.

Sure, I agree, and I've also made the point about Chinese power projection before (with regard to the idea of them supporting Latin American countries against the US). But, firstly, China can do affect more than just the South China Sea - they can hit Guam, they can hit American bases in Korea and Japan, and in pushing the US out of the SCS they may well sink a bunch of ships, which will in turn limit the Americans' own ability to project power. Again, as described above, the US Navy is struggling to keep several concurrent deployments, if their situation gets even worse, their supposed control over shipping is going to degrade.

And secondly, I feel like you're pretty dismissive of what kicking the US out of the SCS would actually mean. There's a reason the US has all these bases all over the place - if they could just do the "work-from-home" equivalent for global imperialism, and run everything from the mainland, they would. But, instead, they've built all these bases - because distance actually matters, and the further away from any prospective enemy your bases are, the more of a logistical burden it becomes to sustain operations against them. The US being kicked out of the SCS and further Pacific islands would be a massive blow, and without those bases any control over the rest of the Pacific becomes more tenuous too.

And as for those bases you've listed,

Diego Garcia

This is not super relevant for conflict against China, beyond potentially basing strategic bombers. As we've seen from Iran, strategic bombardment campaigns, even with all the modern bells and whistles, remain of limited effectiveness, and given that China has a navy, after they're done with the SCS, if they're still worried about Diego Garcia they could try to move on it as well. They could hit it with sub-launched missiles too, plus, they have a substantial fleet of strategic bombers to run their own campaign with - and when you have a specific base in the middle of nowhere to target, rather than an entire country, bombing can actually be very effective, as Iran demonstrated. Also, this being a lone base means it's very vulnerable logistically - again, that's why the US builds a lot of bases, not just one here-and-there, so those bases can operate in a network and support one another.

To some extent one can try to exert control over the Indian ocean from it, but, as described above, the US doesn't have the ships for it - blockading a chokepoint is one thing, you can concentrate your ships in a small space, but chasing ships down all over a massive ocean is something else. And, again, this being a single base in the middle of the ocean means there's only so many assets it can support, only so many ships that can be stationed in it, and the base itself will need to have a whole bunch of resources brought to it too.

Somaliland

The US already doesn't control the Bab-el-Mandeb, despite having a presence right off of it! Like, this is specifically evidence for the US not controlling shipping routes - and if they try to do their own blockade on the other side of it, any assets they deploy there would be just as vulnerable as the Gulf bases were. During the Iran War, the USS Ford stayed in the Red Sea and never dared to actually sail past Yemen.

Greenland or the Panama Canal

Not really relevant for a conflict against China. As I said above, the US would likely assert its authority more strongly in its backyard, but that doesn't matter here - the Americans could build a fucking dome over North America and some surrounding territories and the rest of the world would just... go on. The big worry was the US managing to cut China off from other markets - but with Russia and Iran still standing, China has a pretty big market to the north and continued access to the Middle East (although there's still some infrastructure investment to be done on that end). As we've established, China will also be able to contest the US in the Western Pacific, so they're fine on that end. And with the US weakened in the Middle East and in East Asia, any effort to exert control over the Indian Ocean will be pretty dubious, so access to Africa remains as well.

The US may be able to cut China off from access to South America, but even that's probably only going to be partial - as mentioned above, blockading a chokepoint is one thing, blockading entire oceans or shorelines is another. Germany in WW1 could be blockaded because its shoreline is basically just nestled between a bunch of chokepoints - the geography of South America is rather different. The US could probably manage to control the Gulf of Mexico and Caribbean, as well as the South American countries bordering it, pretty well, but the further south you get the more difficult it's going to be.