All of Europe is about 1/3 of Google's sales. The US is close to 50%. The EU minus the UK is probably more like 25%.

They could certainly rationally abandon the EU market if the fines continue to outpace what the entire EU search market is worth in profit. If you're Google and you can stay somewhere close to break-even on the fines, it's worth staying in the market just to suppress potential competition.

The ideal solution however is the for the US to respond by targeting EU companies, for example Volkswagen and Deutsche Bank (soon to be nationalized as it's collapsing) as two they've already very clearly gone after.