The EU would need to demonstrate that it's teeth are sharp and big enough to actually break the skin on those companies.

Most likely result is Apple/Google/Amazon/Facebook buy them off for some trivial (for them anyway) amount of money.

Just like German car makers bought the EU, in exchange for protectionist measures and to get away with emissions that have destroyed a continent's climate? How come the EU is not looking more inwards, or into Chinese company practices, but instead it focuses on American tech giants? Politics perhaps?

Apple has had a 13 billion Euro tax bill out of it. Google is adding browser and search selection in Android in a pro-active move. I would say this is certainly a show of teeth.