"I don't understand how they haven't yet collapsed economically under those circumstances."
I suspect a lot of it has to do with the miniscule percentage of their GDP that they have spent on defense while living under our protective umbrella. That has given them a lot of money to pi$$ away on useless socialist programs over the years. Problem is that the inevitable has happened, and their systems are going bankrupt. It's just taken a bit longer than it would have if they had also been spending significant amounts of money on their armed forces all this time.