The key question is whether they make non-US-ians move to the Valley to participate. Or, rephrasing, leave their home country to move to whichever piece of YC is cutting the check.

Again: there were 4 countries, total, in the standard YC deal terms. Now there are 3. There are many hundreds of YC companies headquartered overseas.

The standard move in this situation is that you form a US Delaware C Corp and make your HQ a subsidiary.