I don't think I expressed anything about their likelihood of payment - just that they won't stop doing business in the EU.

I think your scenario is a real possibility, but ironically one that would cost the US a lot more than it gains. It's really playing with fire, running the risk of even just 1% of EU businesses and consumers opting for EU services over US ones. And just that 1% represents far more than all of the yearly fines to Google/Meta/Apple combined.