The Arabs are not noted for their superior military skills and expertise. EX: The Iraq Iran war droned on for years with both sides losing millions of casualties. And it ended in a draw; no winners.
The US attacked Iraq and womped them in a matter of weeks. Driving them out of Kuwait. And later took them on again and smashed them again in weeks to oust Hussein. The same Iraq that Iran could not beat in years.
The Israelis had similar short wars against the Egyptians. A seven day one, where they, the Jews, just steam rolled over the Egyptians.
True the US is bogged down in Afghanistan. But that's a country building war, not a nation destroying war. The US is terrible at country building, they have been ever since WWII.
If we were to go into Iran with the idea of destroying its economy and its political base, we could do that in a matter of weeks if not days. And while we're at it their uranium processing plants would be smashed beyond recognition.