USF man power drain is substantial due to Rifles and Paras's high reinforcement cost. You have to make a decision if you want to spend high amount of man power on a second Paratrooper squad or building another tank, as we all know USF needs multiple medium tanks for 1 KT (not to mention Major huge pop cap).
Certainly it is possible to have two Paras late game, but this means you have lost majority of your Rifles, Lieutenants, Captains and tanks.
Hm? Why would you go LT and Cpt with Airborne? Going Cpt with Airborne is unpopular to start with and does not usually synergise well with the doctrine, and getting both Lt and Cpt is a categorically a teching failure on the US players part.
As for the KT....a KT?
I see a KT in one out of 20 games against OKW, give or take and for him to be able to get there you've already lost midgame, not to mention there is also OH.
US is indeed manpower intensive but then again most people tend to micro them rather too aggressively.