There seems to be a lot of bookings for mid July and August going to Frankfurt from SFO. Seat charts are back to normal, no spacing. If the EU ban holds for a month or two or more regarding US residences, those who have already booked non refundable tickets are going to be in pickle. I would assume that UA will have no mercy upon their souls.
The uncertainties of future travel restrictions what change waivers etc. are meant to cover.