If you saw the US games against El Salvador and Honduras, in both places when the US was taking a corner police officers had to stand next to the corner taker holding up their riot shields to keep the stuff that the fans were throwing from hitting the guy who was taking the corner.
You can't legislate against individual idiots, because there are some of them everywhere. But when it is so bad that the police and security know ahead of time that they are going to have to use riot gear to protect visiting players and they still do nothing at all to stop it, that's a problem.
And the US will never join UEFA, so stop it.