I think Canada actually demonstrates why a long-term military occupation of Canada is impossible. The Anglophone population and inhabited land area of Canada are both fractions of the Confederacy. Canada has two major uprisings in two generations, and the methods of guerrilla warfare and terrorism have improved greatly since the mid 1920s - car bombs, people bombs, millions of surplus automatic weapons floating about.
Meanwhile, the US has to build a superbomb arsenal to keep pace with Germany, and keep an eye on Japan in the Pacific, all the while continuing to occupy both Canada and Utah, as well as maintain the social services that Americans grew accustomed to post-GW. Politically, the attitude of white Confederates seems far more hostile and bitter than either OTL Germans, or OTL Confederates during Reconstruction. Even with the remaining Negroes and disqualifying former Confederate officers and politicians, there won't be enough willing to take the oath to re-admit the vast majority of states - probably none other than the former Rad Lib areas.
The US is going to reconcile itself to pulling back, probably within twenty years. That fits with the Civil War parallels HT built into Settling Accounts.