For the purposes of this question:

By "Generation X" I mean anyone born from 1 Jan 1965 to 31 Dec 1980 inclusive, in whichever time zone they were born in.

In case of secessions/revolutions/wars/etc.:

By "the US" I mean "whichever country controls 38°53′23.4″N 77°00′32.6″W" (the current location of the top of the US Capitol dome).

By "president" I mean "head of state" (whatever their official title, and whichever way they are selected).

Resolves NO once everybody born before or in 1980 is dead. I can't think of any situation I would resolve this N/A at the moment. (DC no longer being part of any country the way Antarctica isn't part of any country now would still eventually resolve as NO, not as N/A.)

Edit: in case a country has more than one head of state (like Andorra today), resolves YES if at least one of them is Gen X. If an international border passes straight through the current location of the US Capitol dome, resolves YES if at least one of the countries there has a Gen X head of state. If DC is officially an international condominium, ditto. An AI (deployed after 1980) wouldn't count, even if it's only trained on texts written until 1980. Let me know if you can think of any more edge cases.