I think to sign out you have to go to manage accounts and delete your account. The wording is a bit scary but it’s just removing your user from memmy. The only issue (it might have just been me) is that the add account button wasn’t working, so when I did this I had to reinstall the app to log back in.
Not American but the US had an extremely high tax rate on the rich for most of its prosperous years. It was only recent removed and you now have massive wealth inequality