The problem is that we have spent 40 years adopting US technology, across multiple generations of software developers and decision makers, while everyone was supposedly on the same side.

It will take similar amount of years to go back into the cold war heterogeneous computing landscape of the 60, early 90s.

This assuming there would be an willingness across all European countries to actually push for that, and not jump out when it gets too hard and search for compromises instead.

This is why most sovereignty initiatives focus mostly on SaaS products and hardly on actual computing devices.