Can American businesses actually be sued or anything over GDPR? What if all my servers are housed in america? If I have a user agreement that my users agree to, I don't particularly care what another country thinks about what kinds of privacy they think my users are entitled to. I would already have a legal agreement in that case.
If it is against the GDPR, then it is an illegal agreement in the EU. Non-enforceable contracts are a thing. You are not allowed to literally sign away your firstborn, sell yourself into slavery, or accept a job at less than minimum wage. Enforceability will generally be based on revenue streams coming from the EU (oh you want a credit card processed from an EU user? We'll be taking that money as a payment towards yo…
The last item is nothing like the first two. The EU is now going to see the natural conclusion of a society based on its conception of contract rights. Digital technology magnifies the effect of everything by several orders of magnitude, so I suspect we'll see dramatic consequences flow from the law.