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.
(This comment is a draft and, as such, still subject to change):
But the people who know about these things don’t seem to think that’s a likely threat right now.
Nonetheless I would advise to be prepared in case trump suddenly decrees that .gl is now .us or that there's a 4 million percent tariff on using a .ca domain or some such foolishness. If one can suddenly declare the gulf of mexico to be the gulf of america or lake ontario to be lake america one can certainly put pressure on a single organisation to change whatever they feel like.
As an internet user you can:
create a hosts and/or hosts.BAK file and make generous use of it ^[hosts (file) - wikipedia https://en.wikipedia.org/wiki/Hosts_file]. Think of digital infrastructure you need to use everyday and/or in case of an emergency.
keep a list of functioning dns servers owned and operated by organizations that will likely roll back any nonsensical superimposed changes. Consider local, independent, non-US entities.
when push comes to shove, be prepared to use alternative namespaces such as the one operated by opennic ^[https://en.wikipedia.org/wiki/OpenNIC#OpenNIC_namespaces]
As an internet proprietor you can:
prepare yourself and your servers for such a scenario
register (and use) a domain in an alternative namespace
make users aware of alternative methods to reach you/your services
As a network operator you can:
maintain awareness and ensure preparedness
maintain (auxiliary) digital infrastructure independently on non-US soil