Japan lets Americans come, visa on arrival. If you want to stay longer than 90 days, you can start a business, you have a lot of leeway here, and loans are pretty cheap, like 8% for foreigners, <4% if you've been here awhile. Huge foreign community can guide you when you get here.

If you're in your 20s, you can get a working holiday visa and work for any company that will hire you.

You can't just step out for an hour and reenter like with China, Japan doesn't like visa-runs.

With China, you can get an L(tourist) visa and make a visa-run every 90 days (60 if you applied outside USA), or M visa if you plan to start a business.

The China visa process kinda sucks, dm me if you need help.

For vietnam, you can go there on a 90 day evisa, and if you're white, a fake college degree can have you working as a fake English teacher at a fake English school, for real dong.