I think the hypothetical you posit is wrong, as US doctrine places primacy on air power. In Iraq, I & II, air strikes at the outset destroyed much of the Iraqi armor and spurred a lot of desertion.
I’m not a military and/or Iraq war expert so I don’t want to argue definitively, but I don’t think you can say US losses would have been significantly higher had the Iraqi army had heavier weapons and fighting skills — they’d have needed effective air defense, too.
I think the Ru-UKR war shows the vulnerability of contemporary air forces to air defense, however, and that Western/NATO forces themselves lack cost-effective short-range and medium-range air defense systems. The US Air Force fields exquisite weapons (“platforms”) and these may prove useless in a conflict like Ru-UKR. Or, perhaps, they’re good enough to overcome the difficulties that the Sukhoi/MiG-based air forces of either side have encountered. Hard to know.
Range and mobility in artillery systems also seems like a weak point for the US military. The Excalibur precision shell is very expensive but likely cost effective—one shot, one kill. But the US M777 towed howitzer costs ~$3.7M (titanium) while the French Caesar costs $5-6M and can outrange the M777 in addition to driving away immediately after firing.
