Any group is vulnerable to the possibility of corruption. So to just pick on the UN makes you sound like a hippie who has nothing better to do.
Talamare is right. To focus only on the media-influenced events of Iraq as your argument for the UN being "useless sh-t" and ignoring the millions of people who are able to live another day because of efforts from associations like the UN, make you sound like a hippie who has nothing better to do (aside from comments like "that's so right man!").
The point here is not to say the UN is a group of holy men bent on restoring good to the earth. If you want to change things, it will be to persuade the people who have the power to do so. If the Senate lays down demands for change and action in the UN, they would probably succeed, since the possibility of losing US funding could devastate the UN.
What is f_cked up is that you believe the US is the root of all evil in the world. There is a lot of messed up things in this world. I suggest you get used to it and look for working solutions. Otherwise, don't whine ignorantly or be flamed by people like me.