No, and no.
Our UN veto means that the UN can't place global economic sanctions and embargoes onto Israel, for one thing.
For your other claim, keep in mind that many organizations survive today *without* U.S. membership; so too could the UN.
You would be making a bad gamble, with lives and entire economies at stake, if you played your hand such that the *only* way for you to win would be if the UN folded if we left.
I promise you that Europe, China, Africa, and the Middle-East would *love* to pay for a UN that had no U.S. veto.
How fast could Europe, China, Africa, and the Middle-East organize the same charity effort that we put forth for the tsunami disaster?
>>Our UN veto means that the UN can't place global economic sanctions and embargoes onto Israel, for one thing.<<
Are you more concerned for the USA or Israel becoming a victim?
>>For your other claim, keep in mind that many organizations survive today *without* U.S. membership; so too could the UN.<<
We are the reason why the UN doesn't just 'survive'. We are the reason why they are effective.
>>I promise you that Europe, China, Africa, and the Middle-East would *love* to pay for a UN that had no U.S. veto<<
Then why aren't you promoting the idea that they pay as much as we do every year?.
When I look at what we pay in cash and how much of our military strength or the threat of our military strength is used to 'satisfy' UN needs, I don't see Europe, China, Africa, and the Middle-East working hand in hand to replace us.