Firstly. Iran's strikes didn't carry much of a risk of expanding the war - Israel was obviously all-in from the start, and the Gulf states, while they may have publicly pretended that they were just smol beans, were also involved. Note that Iran did not strike European bases, the move that is always demanded from Russia - the Sofia airport in Bulgaria for example was used by the US and would have been in range even with the 2000km limit that had been imposed by Khamenei, and many other airports would have been in range if the Iranians decided to not abide that limit (since it was not necessarily a question of technical limitations, but political). The two notable strikes on targets outside of US/Israel/Gulf countries that risked this, on Cyprus and Diego Garcia, were never confirmed as Iranian, with Iran denying the later one as a false flag - and given that the Israelis immediately came out with a "see, they could strike European capitals with this kind of range!" statement, it may well have been exactly an attempt to compel European countries to expand the war beyond their basing support. Iran also obviously did not strike any industry in Europe or the US.

In Russia's case, direct strikes on European logistical and industrial sites would risk an expansion of the war - and given that Russia is fighting an attritional conflict, introducing a whole bunch of extra NATO troops would throw off their attritional calculus substantially. As it stands, NATO equipment gets to slowly trickle in as aid and be destroyed piece-by-piece, rather than coming in all at once.

Secondly, as far as the ability of long-range strikes (not of the "bomb all civilians" variety, but actually targeted ones like Iran has done) to defeat the enemy without the involvement of ground troops, which has seemingly been vindicated by the Iranian campaign, there is still an important caveat.

The US is at a substantial disadvantage here as an imperial aggressor waging expeditionary warfare far from home. As such, they are reliant on infrastructure from which to attack - "moving infrastructure" in the form of ships, and permanent in the form of bases. Both of these are a very limited resource - the US only has so many bases in the region, and through decades of decay the US Navy has been reduced substantially so it cannot compensate for the lack of physical bases to the same extent as it could have in the past (for example, for the Gulf War the US deployed six aircraft carriers, while for this war it barely managed two, with one of those having its deployment extended for far too long to likely disastrous effects in terms of maintenance, and that's not even counting the laundry fire... although technically I think there was a short interval where there were three at a time, after the Ford returned for a little bit after partial repairs only to eventually be sent back home for good - so they tried managing three at a time, but couldn't sustain it and had to send the third one home).

So, with this more limited set of targets, it was feasible for Iran to sufficiently damage them to degrade the Americans' ability to fight and make the continuation of the war much costlier, due to the more extensive usage of tankers and fancier munitions in order to compensate for the American planes having to fly from further away. Plus, y'know, the Strait. And in the event of defeat in some peripheral region, the empire can just... pack their bags (what's left of them anyway ) and leave. It would be humiliating and deeply politically controversial domestically, of course, and it could have various consequence for the empire down the line (given that they were presumably in the region for some concrete strategic reason), but it is materially possible.

The Ukrainian situation is different - they're on their own ground, neighboring Russia, not sustaining an expedition continents away. There's way more bases and infrastructure for the Russians to contend with, so it would require a much greater investment of resources to destroy all that (and it would have to be a continuous effort, as infrastructure can of course be repaired - as the Iranians themselves demonstrated), and since this war actually involves a ground component, unlike in Iran, one has to weigh the advantages of degrading Ukrainian performance by denying them planes and industrial capacity with the disadvantages of leaving less assets available to support one's own ground troops in their assaults. Russia's airforce is nowhere near as large as the USAF, and has to juggle priorities a lot more. And of course, in the end the Ukrainians can also keep taking advantage of infrastructure in neighboring NATO countries (for example, a lot of repairs are done out in Poland), for which refer to the first point.

Note that at the end of the day, as successful as Iran's campaign was, it has not stopped Israel in Lebanon. A long-range strike campaign may be able to defeat another long-range strike campaign (by hitting more meaningful enemy targets while preventing the enemy from hitting your own meaningful targets thanks to concealment and keeping assets protected in fortifications, thus preserving your firepower), but a ground force, in most circumstances, is going to have to be defeated by another ground force.