What?! I mean, yes, most coverage of the US isn't exactly positive over here due to mr. Trump, but eh, this really makes zero sense.
I think this is more due to potential terrorist threats at (large) concerts, but those are way more guarded than they ever were since France two years back. Every single day there are major artists playing all over Europe. But the wording implies American's specifically are in danger in EU.
The TACs are planning a trip to Europe (Ireland) this summer. Not sure what to think of this.
You'll be absolutely fine. Obviously the EU is a collection of a lot of very different countries, but I sincerely doubt Americans are suddenly unsafe in most of them.