. I'm also not aware of any country (please correct me on this), that ditched the 9mm Parabellum for the .45ACP.
Branches of service in the United States have opted to either get rid of the 9mm or not adopt it all. The United States Marine Corps Special Operation Command generally issues and uses 1911s. One of the new DIs here just got back to the states. He showed me the pile of Wilson 8rd mags he'd been issued and said his unit had all special ordered a Kimber for when they got back. He still had a Blackhawk Serpa for a 1911 attached to his armor carrier. The Eagle 1911 mag pouches that he had were also quite nice, and had the NSN printed on them, suggesting that they too are indeed an issue (albeit in limited numbers) item.
Airforce PJs also went to great lengths to retain the 1911. New and old ones continue to see use by Army units as well (Rangers, Delta, etc). Several were put to good use in the series of events popularly chronicled in "Blackhawk Down". At least some .45 M&Ps have seen use by the USMC recently and some years ago there was the adoption of the MK23 specifically as an offensive handgun.
So popular is the 1911 and the .45 in the USMC that if you visit the Marine Museum at Quantico, you will see that they have an entire display devoted to it. Venerated might be a better term come to think of it...
Where the .45 loses out a bit is in barrier penetration. It's also hasn't proved possible to develop an effective AP load for it that is capable of penetrating soft body armor, helmets, etc.
Still... a hundred years of anecdotal evidence regarding .45 FMJ (and anecdotal information about the .45 Colt before that) suggests that it works rather well. And that amongst those who have a choice - and could literally have anything they wanted in the world - the 1911/.45 combo still gets picked.
In the lab, we find that the .45/230gr FMJ offers about 18 to 18 and a half inches of penetration in "jello". The original suggestion from the IWBA was 18 or more or penetration (to reliably damage the resilient internal organs in humans). For various reasons this later became the "12" standard most people are familiar with, but they generally forget about the "or more" part of even that.