Edit: I don't want anyone to think I believe it's a good start but it is a kind of solution. I wonder if lots of US companies, once they begin to realize GDPR is a problem for them, won't decide to try one of two things:
1. This: block access from IP addresses believed to belong in Europe.
2. Lobby Congress for a law (or a quick Executive Order) saying that US companies don't have to comply with GDPR.
A few weeks ago on Twitter [1], I speculated about #2. It was too early, I guess. Few people in USA seem to be aware of GDPR at the present time. That'll change in a couple of weeks.