For NATO's purposes with 9mm, I think it's fine in that role. And there are bazillions of 9mm rounds and capable platforms already out there.
Wouldn't bother me to see the US return to .45 ACP, however.
Certain groups within the US have already done so, or never left. If they want to insist on having more than 8 rounds, there are numerous highly proven hi-cap .45 platforms these days....including those of the 1911 variety...
Mauser Werke, Schmidt-Rubin, Colt, Walther, HK, Weatherby, Browning, Ruger, Savage, Bushmaster, Marlin, Mossberg, Saiga, S&W, Sig Sauer....a few friends of mine