What if the US goes to war with Iran? (and Iran had China and Russia as allies)

Would Uncle Sam lose? I mean, I'm not trying to sound like a doomer but with massive debt piling up and the military spread so thin around the globe I can't help but wonder. China and Russia are already heavily invested in Iran's natural resources so it would be in their interest to ally with Iran. With the US economy in the tank while China's economy is booming, how would America finance a war like that? Also where would Europe fit in? You're welcome to tell me it won't happen and why, but humor me for r/conspiracy's sake.