Have you thought about the fact that the Americans are strong not only by its army, but due to the armies of its allies.
Which ally are you referring to? The European armies have become a laughing stock around the world. The Saudi Army has very expensive equipment, but the soldiers don't know how to use them. Only Japan is having a strong army, among the allies of the United States.
As long as it is enough to hold russia down all is good. No need to waste money
