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?
You then hope you don’t have any assets in a part of the world where the EU member states have jurisdiction over you and can seize your stuff to pay your fines. You should also prepare to have your site blocked for any traffic comming from within a member state.
In short: Unless your entirely US based, setve only US or non European customers, and don’t plan on ever expanding into european territory, there probably isn’t all to much you can do legally.
This is the best response, imho