If compliance is impossible, it's probably because your business model is incompatible even with the spirit of GDPR - the notion that a person should have control over their data and other entities should handle it with care.

If compliance is expensive, it's probably because your business profitted somehow from handling personal data (or you let someone else reap the profits, e.g. tracking ad networks).

I find your situation similar to the one of an engineer in a chemical plant who got the task to make the whole place completely ecofriendly due to new regulations. The solution to just block the EU and resume business elsewhere is the best course of action if complying is indeed impossible or infeasible for your business. If your organization decides to gamble because there is still profit to be made in the EU, it's on them when enforcement comes around someday.

In any case, competitors will find a way to offer GDPR-compliant services and there might be enough demand for data protection laws in the US, changing how businesses have to deal with personal data. Time will tell.