Pre-pandemic, a group of Windsor Flying Club members based at CYQG made an annual excursion to the Bahama Islands from Canada. Our experience with the U.S. controllers is that the further south you go the more trouble the controllers have with our Canadian call signs: more letters than they are used to. We fly VFR and use flight following.
I have observed similar befuddlement by US controllers, becoming greater the further south I went with my Canadian-registered aircraft. A workaround which helped was to deliver the call sign carefully, with a modified first letter: “Canadian Golf”, pause, “Alpha Bravo Charlie”. Many of the controllers could at least reply with the “Alpha Bravo Charlie” part. And of course the controllers near Canada (KBLI, Seattle Approach, KGTF) had no trouble digesting all the letters.