A quick Google search will show otherwise. In about 60 seconds I learned that the UN gave a speaking place for the Americans during the Cuban Missile Crisis, and embarassed the Soviets into retreating from Cuba. The World Health Organization has saved millions of lives, including those saved through the eradication of smallpox (organized by the supranational WHO). The UN has hundreds of accomplishments under its belt.
The UN certainly has major problems and needs to be reformed, but to say that they are "A Piece O Trash" is to deny reality.
Regarding Jerusalem, I think it belongs to humanity as a whole, and that no one country or race can claim it. My $0.02.