This is exactly what I was coming to HN to query about. Without some agreement with the US federal government, I don't believe they would have any mechanism of enforcement that would affect your business in the U.S. I imagine they could do something like block your site from EU ip addresses but nothing like coming after you or your company for damages.
This sort of argument is like saying you can commit murder then flee to Algeria, and the US will have no mechanism of enforcement. It's true, but heaven help you if they figure some mechanism out.
Technically true, but what does the enforcement action actually look like against the small town ice cream shop that doesn't know or care about the rights under the GDPR of a tourist from Spain?