re: And your country
"But why can' the US just leave now?
The first and foremost reason (the one perhaps citizens outside of the US can better understand) is that it would look like defeat and be much too humiliating to the US.
But look at all the savings you could do!"
Here is your homework assignment:
Go find someone over in Europe who has clue about international law and ask them, "why can' the US just leave now?"
Over here in the backwater of America we know why.