A few things to add some nuance to this discussion:
First, the USA is not easily described as a single, monolithic entity (not unlike "Europe"). Yes, cases are rising in parts of the USA, but not all; and in fact are way down in the east and northeast. If the goal was to "flatten the curve", the east coast states and Illinois have - up to now - done that every bit as well as any other locality in the world, given the severity of the initial outbreak. While I can't think of a reason to come right now, New York - where I live - is probably as safe a place as any if the question is about transmission rates and infrastructure available for a medical emergency.
Second, the west coast had a very low number of cases at the outset through last month, and it is possible that their increase derives from increased mobility over the past month or so from east to west. Remember, the "European strain" of the virus is what we have on the east coast, which is not the same strain found initially on the west coast (the "China strain"). These vagaries will be important as the days go on, but anyone trying to predict what the west coast looks like in the next four weeks is just speculating.
Third: Florida. It is apparent that their laissez faire attitude toward reopening has increased the number of cases and hospitalizations. Same with Texas. I would avoid those states because, quite simply, their curve was not and never has been flattened.
Finally, on the broader question of border closures and reciprocity. I note that many say "I wouldn't let Americans in at all, given their virus stats". To that, I say see the above. The only way to ensure that the curve doesn't explode again, wherever you are, is to require testing. Yes, it can provide false negatives. No, it doesn't necessarily show you what someone will look like in three days. But if a country is trying to mitigate transmission and infection rates locally, testing a visitor before departure and showing the test result on arrival is the most effective way of doing that. A blanket ban on Americans or Europeans or any nationality is a throwback to the days before we had science. As a New Yorker, I am more likely to be "safe" than a Swede. And I can be tested if you ask me to be (see Iceland)
I am all for open borders, but if the ultimate goal is to keep transmissions low, test test test. I don't care where you live or what your nationality is. If you test negative up to 72 hours before departure, I'd be willing to place a bet on you. Tens of thousands untested tourists from "safe Germany" or "safe Spain" or "safe Italy" or "safe Austria" (as an example), regardless of their potential virus status? Not so much.