Forget all the stuff out there that says the GDPR protects EU citizens. This is a question of jurisdiction and enforcement. Say I run a blog under a business registered in the US funded by advertisers in the US. A EU citizen that comments on posts issues a GDPR request that I ignore. Their government fines me. I tell them to get bent, I am out of their jurisdiction. What can they do at that point?
There’s a treaty between us and EU.
So if you suspect a us entity violating your EU right aka gdpr you can make a complaint to your city’s data protection agency or directly via the EU complaints for cases outside your country ( inside and outside EU) They will take care of it and make sure that you don’t need to travel to another country for court stuff and more ( if needed in most cases you don’t)
Usually it gets regulated in a way that you can go to a court in your city and the enemy in his city.
So all in all the us wants the EU market and vice versa so both agreed to a treaty to honor the rules of each other
More info google
Trans-Atlantic Data Privacy Framework