"American Companies" is a pretty arbitrary measure these days - both domestic and abroad corporations are gone after by threatening (and carrying out depending on the judgement) to restrict domestic business and seize domestic assets. The US doesn't really have legal standing to seize assets of Google in their London offices (though the UK may be happy to run an assist) and the EC can't seize property in Mountain View - but Google is international and has assets in most countries that can be seized - for them the bigger threat is probably a restriction of business if google search were to be banned in the eurozone[1] then there would likely be a reverse network effect that led to a loss of traffic globally - it wouldn't be unlikely for a lot of browsers to pull google from being a default search engine.

So, the EC has teeth they can use to enforce here - but more importantly google also wants to minimize how much they piss people off. Hence a PR stance of "Hey, we're sorry you feel that way - is there anything we can do to make this go away faster?"

1. I'm not saying this is likely or makes any sense for this particular probe.