It's more of a case of too few combat forces for the missions out there. Rumsfield wants to uber-tech the military, but in the final analysis, it's ALWAYS boots on the ground that win wars. And we really need about 6-8 more infantry divisions, and 2 more Marine divisions. . .
I won't even begin to address the argument that our heavy reliance on mechanized forces has ominous parallels with that of latter-day Rome: Rome only began to lose its' greatness when it began to rely on mounted forces, as opposed to legions.
In the end, it's ALWAYS the infantryman that will win you the war . . .
And when the demographics started to crash, coupled with a massive influx of non Romans into the empire who would not assimilate.