Two things that are not very important:
- the first version of the maple-leaf roundel was introduced just after WWII, by 1947 at least (
http://www.canmilair.com/schemes.htm; http://www.vintagewings.ca/VintageNews/ ... nd-Up.aspx)
- I'm not sure if custodian helmets (worn by Canadian police until just after WWII) were pith or cork; sources are inconsistent - so "custodian" probably better - tho' if Turtledove calls'em pith, who are we to disagree?
I haven't read Turtledove's books, so any criticism has to be muted, but I've found one of the key aspects of this timeline - that the U.K. would ally itself with C.S.A. - unlikely. British public opinion was so anti-slavery that it not only abolished slavery in the Empire, it interdicted the Atlantic trade with the West Africa Squadron - itself a remote cause of the later Civil War. Tho' Britain's textile magnates wanted cotton they were also themselves fairly liberal in our terms; during the OTL Civil War Britain could at best be described as torn; certainly not pro-CSA. But, as I say, I haven't read the books, so perhaps Turtledove squares this circle.