That seems like a lot, but when you're talking about a sustained deployment it isn't. There are a lot of people who are in administrative or infrastructure related jobs. Then we've got people we have to keep in other threat areas. WE're not pulling any of the 25-35k troops in Korea for Iran. And soldiers can't stay there indefinitely, they have to rotated in and out. And, there are limits to how long you can deploy soldiers. There's a reason the military had to reduce enlistment requirements during the Iraq War. They were hurting for bodies
And, what happens when you start deploying reserves? These are people who are basically part-time military who work full-time jobs. You start touching those assets and it's crazy disruptive to their lives. So, your reserves numbers start dropping off because people only go in the reserves thinking they're going to fight if a WAR happens, not some adventurism bullshyt.
And, just like another poster pointed out, we had maybe 150K max in Iraq, but there was another 100-150K in theater in support roles. And, an Iranian invasion would be much more difficult than Iraq was. Never mind that we'd probably be going it alone.