They'll be fined millions of not billions. The interest will add up on the fine if they don't pay, then assets will be ceased. This isn't a reasonable way to do business in Europe. Either follow the law or effectively shut down.
I don't know the details and decisions of my company, but I guess I shouldn't travel to Europe in that case.
There are multiple things that could be done. The EU could deny entry to employees of the company. They could ask the country of the company to press charges there. Of course the country could also ignore the EU, but than it would risk its good relationship with the EU.