Incidentally, crypto exchanges in the past (and one very recently, known as Bitmex) have faced issues with US authorities regarding this. Context: US citizens cannot trade unless the exchange is US-licensed.
Essentially, US gov applied pressure such that a simple tick box (to prove you are not American) is not sufficient. So, authorities definitely have precedent to enforce geo-constraints, it's just a matter of "do they care".
Essentially, US gov applied pressure such that a simple tick box (to prove you are not American) is not sufficient. So, authorities definitely have precedent to enforce geo-constraints, it's just a matter of "do they care".