The attack on Iran will come in 6 months time when nations have gotten off the reliance of Iranian oil. If you aren't smart enough to take the hint now, you are going to suffer a major problem when the taps run dry.
The problem is, Iran has already calculated this. I am not talking about their stupid mullas, but rather their strategic division. Remember, while defeating them won't be a problem militarily, you and rest of NATO will start a world war for no reason. With its last hope of resisting an external invasion, Iran will launch missiles into the Gulf countries that supply most of the oil to the rest of the world on this side. Think about the ruckus that would cause. Most people living in Gulf are expatriates that will suffer and mostly it is our people. This would naturally put pressure on our government to take action against Iran for a reason that they're not directly responsible for.
Trust me, this won't be pretty. The same for Chinese whose oil supplies would be affected from Iran and they would rather go much more aggressive and would target NATO more than Iran. NATO is not in a condition to fight China head-on.
With prices of oil going through the roof, NATO will only invite military retaliation against itself. Iran as of now has that advantage. While they might ultimately lose the war (due to their limited military), they will ensure most economies are under severe crunch. All while European countries will totally collapse. Nuclear energy for electricity around cities is fine, but oil is needed for almost everything else; transport, supplies, fuel burn, aviation industry, mass transit etc.
Do you even know what would a war directly against Iran escalate into?
Even if we and the Chinese do join the embargo, it will be hell for this region while USA will be sitting tight on oil from Venezuela and Canada.
Don't look at what US will gain; see what we including Europe and Asia will lose.