You have the right idea. The special thing about the US federal tax is that it covers everyone the law covers. Most countries tax residents or some other subse

You have the right idea. The special thing about the US federal tax is that it covers everyone the law covers. Most countries tax residents or some other subset, perhaps "residents old enough to work", you get the idea. The difference is the set of people who are subject to US federal law for a reason other than residence. There are things you can do that bring you into scope, including some forms of work.