I agree with rebelcowboysnb too - probably for the very first time.
NCReb, your summary of the relationship between south Korea and the US is exactly right.
As for abandoning friends and allies, well there are plenty of precedents. Vietnam, Iraq and, soon, Afghanistan, for example. Vietnam did quite well but the other two are disaster areas.
Also WW2 was because of alliances. Turned into a larger conflict than needed to be because of alliances.