It's fucking lonely, that's the main thing. You can't build meaningful relationships, you can't establish a home base, you can only travel with a small amount of items, language barriers are a killer (even in English-strong countries), and the hassle of moving place to place, vetting long-term rentals, meeting hosts, etc consumes much more time than you'd think. It's great to travel, and I do love the aspect of doing that. But I think it's better to travel to places 1-2 weeks at a time with a girlfriend/friend with a proper hotel than do this.
Now I want to share my perspective as an American. These past few months have also made me more grateful for being an American. I like Europe, especially Vienna, my favorite city besides Reykjavik, but America is better in many more ways than I realized. People are nicer, food is better (I didn't actually thing this would be true but it is. I'm in Italy and all I can think about is how the Italian food in America is better), dating is easier (European women are strange, still figuring them out), alcohol is WAY better. I also miss private car use more than I thought I would, car-based infrastructure can be ugly but with a car, you really can go anywhere without having to wait for the tram/bus.
There are definitely objectively better parts of Europe though, namely coffee, history, food quality (as in ingredients rather than taste in this case), city safety (this is a big one, you can mostly relax in European cities while in America you always have to look over your shoulder), demographics, museums (but that's more useful to a tourist than a resident), infrastructure quality, and some other things.
So I'm torn. One thing I know is that I can't keep doing this moving around thing, I need a place to call home. My actual home (North Carolina) is pretty great, but I would love to live in Vienna longer term. Thing is, I have no clue how to get a visa that lets me stay longer. Anyway, I'm out of space, thanks for reading my blog.