At least one .org website that I know of has been shut down because the USA pressured the US organisation that controls the .org domain into doing so.
They could repeat this at will for quite a number of sites.
An immediate step to prevent this possibility, if you run a website, is to register a domain that is controled outside the US.
I have not found one article that just lists them all, and who controls them, but most TLDs have their own wikipedia article, e.g. .org (US controled), .eu (not US controled, yay) etc.
Ultimately ICANN controls all of this, and that's a US orga too, and Trump could bully them into doing shit, too. But the people who know about these things don't seem to think that's a likely threat right now. Also ICANN seems to defer a lot of tasks to exactly these TLD orgas. After all the internet still is (somewhat) decentralized.
Of course, ultimately all of DNS is controled by ICANN, a US orga. Trump could effectively shut down the whole internet, we’d have to revert to numerical IPs. A scary thought.
I understand the sentiment but that is not effectively possible. It is not ICANN that de facto controls domain name resolution, it is the name servers that are spread around the world. A supranational organisation such as the European Union, or countries like Russia and China, can have their DNS servers continue to resolve domain names to the correct IP addresses regardless of what decisions ICANN or other TLD ownership entities make.