Europe having its own Microsoft might be better than Europe having to use the US one and sending it like $100/user/yr in whatever subscription they've tricked them into.
Europe doesn't have to use the US one. It's been the easier choice historically, but there's little beyond inertia forcing Europe to stick to Microsoft. Not that that inertia isn't nothing though.
There is also political lobby and even more importantly local businesses that are build around microsoft. From one person to huge companies all exist to support microsoft. It would be extremely costly to retrain/regear everyone involved. So the inertia is huge.
