I've been thinking about the same thing, even been making a few butternut skins for Heinkels and B-25s. Made a St. Andrew's cross for their battle flag with the intention of using it as their decal...
...but it's too small I think.
From what I read, based on the aircraft described, I got the distinct impression that the CSA 'Mules' were essentially just Ju-87s, the US Turbojets were essentially Me-262s (even down to their troublesome engines and vulnerable landings). The 'Asskickers' were pretty vague, but it gave the strong impression of a strong winged monoplane (maybe along the lines of a 109 or something Spitfire-esque). I thought he referred to the IJN planes as Zeros and the only real life plane I remember were the B-17s mentioned by Flora Blackford, on their way to strike Richmond... or something. Got no idea what the artillery spotting 'Grasshopper' was.
Based on these observations, you could suggest that maybe the US aircraft industry of the day was influenced by is larger, more influential ally, the Germans. Or maybe these were just specific examples used to tell the story. Although I do like the idea of the British influences of the CSA and the possibility of CSA Spitfires and Hurricanes too.
I'd be interested to see the Tsar's air force and it's technological developments (or possible lack there of...).