Was I accepted?
It's not my job to accept characters or any of that, but I can provide some feedback; your character probably, in order to be an officer in the United States Army (since 1944 saw a lot of Americans in the UK; WWII) needs to be a United States citizen, so it's probably best to say that his father was an American servicemember and his mother is British, and sure, born in the UK -- not a problem.
If his father was from the US, odds are he was a GI or an officer. If you want me to shake and bake information like unit and background, I'd be happy to help provide that sort of fluff.
As to being raised in the UK, I'd say that right after WWII, the UK was rationed and going through really hard times whereas the United States was having an economic boom, so it'd make sense that the family would move back and he'd be raised primarily in the US, which is why he'd go to a college/university in the US and commission through Reserve Officers Training Corps (ROTC) which was a booming business in the Vietnam years -- they needed as many college boys to turn into butterbars as they could lay hands on.
The M-14 is an unusual choice for an officer, in that the weapon is fairly heavy to begin with (depending on the officer, they might be more worried about weight savings than the full power of an M-14) and also in that Air Cav were early adopters of the M-16 (because it was light and handy when mounting/dismounting aircraft in airmobile operations) and the Colt Commander tends to be a piece that colonels and above, often staff types, might carry if they weren't expecting to go into the field. An infantry officer at the junior grade would probably be more reassured by packing an M1911A1 (which, admittedly, has been over-issued in this RP... ;) ). The place you're most likely to encounter M-14 is Army combat engineer units (infantry gets first pick of the M-16's), possibly Navy types on the PBR's in the Brown Water Navy and Marine rifle units because the the Corps had (have) a cult of accuracy and a lot of them preferred the M-14 to the M-16, which had a bad reputation in some circles.
That's not to say of course, that there aren't a lot of options for an officer that wants something lighter. M3A1 grease guns are totally around, and they use .45ACP which is an issue item in Vietnam for the Army. There's more exotic stuff, but keeping it fed with ammo is a bigger problem and that sort of thing tends to show up in special operations units...and not even all of them. MACV-SOG recon teams, SEAL platoons and Army Special Forces units had access to a lot of interesting shit, but they still had a hard time arming their recon teams with Colt Carbines because the Rear-Echelon Motherfuckers (REMFs) tended to take them (and the jungle boots and other shit intended for infantry use) as their personal trophies to show off what a badass they were while the grunts sweated in wool uniforms and all-leather boots in a stinking jungle.
Also, binoculars, map, compass. These are very necessary tools of an infantry officer's trade.
But the big one is this; the US Army doesn't just commission random Brits to lead its infantry outfits.
Just my view on where you can tighten up the character sheet, though.