China is trying to steal territory from the Philippines, they arguably don't have the power to fight China. Without allies in the USA they'd have no recourse.
If every country was equal I'd agree with you, but they aren't, so we need protections for the smaller countries out there that get rolled over by the big countries.
Edit: Ideally we wouldn't need a police force, and I don't use Police force to mean what the US is doing in the middle east. I'm all about anti-interventionist policies. But I also don't want to see big governments roll over smaller ones, I think the UN is a good counter to that.
This is what I meant by South China Sea. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&c... Hopefully that link resolves correclty.
