Is there a mechanism the EU could use to inhibit acquisition by a non EU entity?

There is in France. They have a government investment arm that will invest relatively small amounts but with a string attached: a veto on any majority acquisition. This was used for instance to block the takeover of Dailymotion by Yahoo iirc.

It's a double edged sword: it may help in some cases but it hurts the investment scene overall because an exit to the USA is what most EU investors dream about because their returns overall are pretty crappy. Fragmented markets are a lot harder for investors than uniform ones.

It’s not a matter of mechanism. It’s a matter of mindset. Until today the mindset wasn’t there. Maybe this will change.