> We have a photo taken while traveling together in Belgium with 2 other Americans, what server?

EU GDPR is pretty clear that all of the cases which involve transferring data from the EU to the US fall under EU GDPR rules. It refers to the location of the data, not the citizenship or residency status of the individuals who are involved.

So, the photo that you took and uploaded within EU borders is theoretically in scope for EU GDPR - even if your French friend is not in the photo.