The E.U. has no legal authority or enforcement mechanism to stop foreign, online companies from not doing business in the E.U.
E.g. the right to be forgotten, EU has it US doesn't. sanctions when you forget to disclose a massive data-leak on your private escort website? $0 in the US, hopefully very expensive in the EU. Your nemesis publishes lies on the net? EU helps you have that deleted. Your supermarket tracks your shopping and knows you are pregnant before you do (this happened in the UK!), won't happen anymore in the EU. Shady Sunshine Ltd bought your email address and purchase data to spam you, bad and expensive for them. facebook won't allow you to continue unless you agree to face-recognition? This might be the first case in courts.
Wait and see for the good sides once the panic has quieted down.