A)So you want the US to allow Iran,and their nuclear program, to fester like the malignant cancer that it is. This is a country, that for the past 25 years has had an Anti-America day. They will destroy the US at the first opportunity they have.
B) Who says their only interest is a land grab? There is credebile evidence to suggest they can use ICBMs against the US. Or like I said earlier they might develop suitcase-nukes which could devestate the US.
C)With the aid of Russian tech, any military action will be that much more difficult.