If the enemy is far enough away that the extra accuracy afforded by a 1911 would make a difference, you should have been using your rifle.
It is a bit disengenuous to say that a double-stack 9mm has more damage potential than a .45 single stack. Add up the actual weight of the bullets (115 gr vs 230 gr) and actual cm3 of tissue damage potential and see if the difference is really that lopsided?
I also believe the 9mm to be 'good enough' in the man-stopping department when using premuim defensive hollow-points. BUT REMEMBER, we are still pretending to follow the Hague Accords (which we never actually signed) which means that when our soldiers carry a double-stack anything in 9mm, it will be loaded with 115 gr fmj. At least if it were a .45, 230 gr hardball is a well-proven manstopper. And yes, while I prefer 1911s, I would obviously take another good .45, such as a USP, a Glock 21, etc.