Don't worry at all, just assume everything will be back to normal by next summer. Perhaps even earlier, but why worry if you don't want to travel before summer.
There is at least 1 country in Europe where US travellers are already welcome(as long as they can show a negative COVID test): Croatia
https://www.goodmorningamerica.com/travel/video/american-tourists-visit-croatia-amid-pandemic-72025247
"Anyone want to speculate on when the US will be allowed to visit again?"
I bet that US travellers(and other Americans) will be allowed to visit EU countries(and many other European countries) even in this year with some restrictions(negative COVID test).
Edited: 29 July 2020, 10:00