If the Iraqis force the U.S. to withdraw their forces from their country, if the Gulf States say they won't support a U.S.-Iran war and refuse to allow their territory to be used or grant flyover rights, and if the Turks refuse to allow the U.S. to use Incirlik air base to prosecute the war (the Turkish government was already talking about throwing the U.S. out of Incirlik before the current crisis), will the U.S. be able to invade Iran? I guess the U.S. could stage its invasion from Afghanistan. The Afghan government might not approve, but it isn't in control of its entire territory. But that opens up even more logistical challenges, like getting the approval of all the other countries the U.S. needs approval from when they move supplies and equipment into Afghanistan, and launching a war from a place that it itself a war zone.
The American public just assumes that the U.S. can prosecute a war against anyone on the planet whenever it wants without facing any logistical barriers. But that is not how it works. The U.S. took about 6 months to move its forces into position before the beginning of the 2003 Iraq War, and that was with neighboring countries who were willing to cooperate with the invasion and after years of the Bush Administration working to build a coalition and shoring up allies to gear up for a war. The Trump Administration has done none of that ground work, and is not going to have the support of any NATO allies, or many of Iran's neighbors.
The American public just assumes that the U.S. can prosecute a war against anyone on the planet whenever it wants without facing any logistical barriers. But that is not how it works. The U.S. took about 6 months to move its forces into position before the beginning of the 2003 Iraq War, and that was with neighboring countries who were willing to cooperate with the invasion and after years of the Bush Administration working to build a coalition and shoring up allies to gear up for a war. The Trump Administration has done none of that ground work, and is not going to have the support of any NATO allies, or many of Iran's neighbors.
