Most European countries, have their own version of consumer protection agencies, usually any kind of complaint gets sorted out, even if takes a couple months.
If they fail for whatever reason, there is still the top European one.
Most of the time I read about FTC, it appears to side with the wrong guys.
For things like sign-in, you barely have to mention the use of cookies on your website, because it's necessary. For things like items in an anonymous shopping cart, a simple "adding this item to the cart when you're not logged in will cause the item to be saved in a cookie so we can remember it later" would suffice.
I'm not a lawyer, but that's my understanding.
That's why there are websites without cookie banners, like GitHub. It's not even hard to do that; it's just that most companies don't bother, because they know the EU will be blamed anyway.