+1 on this request, not sure if possible though.
If you enable separate USA Postwar country in config files (I don't remember exactly what was that, regiments.ini probably, use SFS extractor on archive containing decals and search for FC mod components if you're interested) it results in all planes using generic USA markers with international default skin version, resulting in US planes looking ugly. Solving that would require rewriting respective classfiles for all planes using different deffault skin for us nation to include na nation, which would be pain in ass to do, it's easier to just branch na from us in FC. With 4.12 coming and seemingly better relations between community modders and TD (and hopefully easier adaptation of mods) I doubt anyone would take this. Especially that it'd require a large scale informational campaign to make other modders write their classfiles for US planes to support FC. Remember that some of guys on Aviaskins may understand what we write here just as much as we understand what they write there.
As for other blue US forces, I would be all for it as well, but only if someone modified the country selection for planes in FMB interface, bc currently, with lack of search function or country>regiment tree like in QMB it requires to scroll (often several times) through a shitload of regiments just to find a country we're looking for (especially when we look for 1 regiment country). Until this works better I can live with only USAF on blue side.
EDIT: Solved gramar nazi attacks, sorry for that... I've slept 4 hours of last 48...