It depends on the specific nature of the conflict. Not every conflict is about control over land; Iran is a perfect example. Their missiles provide a credible threat against globally critical infrastructure, which gives them a way to retaliate without committing ground troops. And their drone strikes are using heavier one-way drones, not FPVs, which wouldn’t make a dent in oil infrastructure or tanker ships.

The current US force configuration was designed to fight quick wars against opponents who mostly can’t fight back. It’s a military built to play “global police,” and for a short while this was probably the correct configuration.

Building a military that stands ready to fight any kind of war is probably impossible—it would be too expensive. You need to look at the biggest threats and optimize for those conflicts. The problem that the US now faces is that rival nations have optimized for defense against its particular style of maneuver warfare with heavy air bombardment. Air defense (not missile defense) is better and cheaper than ever.