It's an unlikely scenario - but block your domain, block bank transfers (not for small offenses, though). "Ask" any EU based payment providers (pretty much all have offices in the EU) to stop servicing you. You can use crypto currencies and the like but the inconvenience is there.

Then probably (or your employees) would not like to visit the countries there, etc.

Technically you should not be selling electronic services in the EU w/o EU VAT, so that already is sort of a breach... but no one chases so small fish.

>> If you run a small US company with a few hundred paying customers and low single digit EU customers, how is the EU going to penalize you?

By forcing EU ISPs to block your ip.

It might be worth specifying your co. is for US users only in your TOS until you are more attractive to European customers.

Maybe put you on a naughty list and inhibit internet access - as the UK does for TPB, et al.?

I don't know if they can.

But if you're a VC funded business aiming to "change the world" and grow big, then it might be a problem for you later.