Yes, but doesn't the checkbox you mentioned, does exactly that, force the users to ignore their rights for the sake of using your site? If this would be acceptable, it would put GDPR into position of cookie law nonsense and if I understood ICOs correctly, this doesn't create a consent as user had no free choice. There is a human rights interpretation here, for example, if we create a contract, that I will be your slave and you give me a car in return, it is quite simple for me to sign it, that contract would be void even if you prove, that I signed it.
The ICO put a market of live human organs as example.
In same manner, even if I would click that I agree, that your site is designed for US privacy laws and not for people under GDPR protection, it would be the same as you would warn me, that I will be your slave before signing and that I can
just walk away and don't take the car. But if I take the car, the contract would still be void. I don't think that this would fly.
The problem is not in the GDPR requirements but rather in right to privacy as fundamental human right and GDPR is just an advice how to respect it - it is actually a free help.
What you want to avoid is something much bigger than the checkbox on your site or ip blocking, check here "The Bill of Rights":
https://en.wikipedia.org/wiki/Fundamental_rights
This is something you shouldn't even think to violate, not to EU or US users. Or anyone else.