U.S. Doesn't Back Call for Iran Expulsion

I don't understand what Iran is trying to gain by stating they want Israel destroyed or even by building nuclear weapons unless it's for bragging purposes. If Iran nuked Israel, I'm sure a number of nuclear bombs would destroy Iran as well. I don't see a winner in that case. Both countries have been eliminated. However, I am wondering if Iranians would be happy if their death took out Israel even though the Middle East was a nuclear wasteland. It wouldn't matter to me that much who was kicked out of the UN since I was thinking the UN should be done away with in the first place. I believe the purpose of the UN was to help keep the peace so if it keeps countries talking, I suppose that works.