> the bigger fear I have is that if such an EU alternative is successful that the US incumbents will swoop in and buy it

That's usually what happens indeed. There is a lot of great tech coming from [the rest of the world] and being bought by the US.

> the cost-to-switch is more important right now than the details

I kinda disagree there. The lack of competition is the problem today. If, instead of AWS, there were 50 services all over the world and companies were distributed amongst them, then it would be much less of a problem. The problem right now is that the US can bully entire countries because those countries 100% rely on US services.

Instead of building a European replacement for AWS, I would like to see open standards allowing companies to easily switch, and different providers competing behing those standards. Or even better: companies could even mix the services: say "I want my backups replicated between this French company and this Croatian one".