They can tell whatever they want, but it would need to be a US court (in that case) who would do the litigation. Which they won't.
> The US does do that kind of thing though. As a dev, break some law, step foot in the US for a conference, get arrested
yes, this is why I mentioned that my point is only for local businesses. Travel or business in the EU can/will be problematic.
> Heck, I was in Mexico and I couldn't login to my provincial government tax portal. There are constant security issues with those sites.
Blocking for security is another thing. Maybe a good idea, maybe not - but that's another story.