Yes, if you're not willing to comply, that's exactly what you should do.

OTOH it just shows your remaining customers that you're willing to do shitty things to them, as long as America is trailing in privacy legislation.

Geoblocking IPs is not a solution, unless you're willing to let some people slip through and block people who you don't need to block. Also, not everyone connecting from a EU country is a citizen thereof.

GDPR doesn’t just apply to citizens of EU countries, it also applies to residents and potentially people just passing through (e.g. changing flights at an EU hub).

Given that the average small-to-medium sized business in the US is unlikely to do any business outside of the US, I think we'll be fine. :)