You'd have a hard time re-entering the usa after automatically losing the case by not showing up at the courthouse and not paying the bill. But in any case the scenario of leaving the country is not unique to airbnb and exists for rental cars, other loans, and basically any activity involving borrowing something

Actually intentionally trashing place at 1M level is criminal offense (vandalism/destruction of property) in pretty much every state, local police will most definitely open criminal case and it may even rise to the level of extradition (and UK has extradition treaty with US).

If you intentionally trash the place at a few thousand dollars level then year - nobody will probably bother other than banning you from AirBnB for life. One time we sort of trashed AirBnB (my 2 year old got hold of pen and draw on the wall and couch while we were not looking) and the only consequence was paying 400 or so in fine (max liability on listing) and stern letter from AirBnB that they may ban us if it happens again.

It's true, you can commit crimes and flee the country consequence-free. You found the loophole. Close it up boys, we're done here.

Nothing, your airbnb account is banned, they'll probably try to bill your credit card, but not much.

You can send a fee request, but mostly you do that to show airbnb you tried and they'll maybe compensate you if they agree.

You're making a good argument for the reinstitution of debtors prisons.