> What the EU gonna do then?

Seize or terminate their patents and copyrights. Issue arrest warrants for criminal evasion. Compulsory licensing of x86 to a European design firm immunized by EU law.

> Perform rapid continental ARM transition

Yes.

Windows is on ARM. Apple is on ARM. AWS and Ampere make decent ARM servers. You have decent x86 user-space compatibility on ARM laptops. That is all users want.

I doubt it will cost 'mythical amounts of money'. Most users use a web browser and an office suite. I doubt they will know a difference for a while.