I have a business contact in Canada whose father was in the RCAF prior to and during WWII.
He was actually folded into the USAAF for a period right after Dec.7th, 1941 and assigned to units in Alaska. Evidently at the time this was not widely known and was kept quite hush-hush.
Later after being reinstated in the RCAF, he went on to England and Europe.
Interesting story... sadly now lost. (His father died of cancer in the 1980's traced to shrapnel that was never removed in his back from the ETO.)