Dude, you don't even offer strong evidence to back up that Hart carried the feud. So let me break it down for you. The whole thing stemmed from the Bret Hart versus Stone Cold Steve Austin match where Austin was able to make a slight face turn due to not tapping out to the Sharpshooter. Now it could have ended there, but Stone Cold refused to drop it and came after Hart every chance he got, which changed the norm for feuds.
Think about it. What was the catalyst for the face and heel changes for Stone Cold and Hart? Was it the fact that Bret Hart won, even though Stone Cold did not tap out in their match OR was it the fact that Stone Cold refused to tap out and passed out, even though Bret Hart won the match? Now everyone has seen Bret Hart win a match with the Sharpshooter and it was the boring old norm. But why did this particular match change things? Because of Stone Cold. And they play up after that of Hart being mad that Stone Cold go applause for lasting helped him as a heel. But if it were Hogan, Michaels, or anybody else, nobody would have cared much.
And what happened after that? Well Stone Cold refused t drop it, as every past opponent who had lost to Bret had done. Bret needed to get reinforcements as the crowds were behind Stone Cold and thusly the USA versus Canada feud was born. Look at all of the USA versus Canada angles before that and after that. They were lackluster. But Stone Cold's obsession with Hart is what drop the popularity of this one. As far as other countries eatting it up, the main country that popped loudly for the Canadians... was Canada! Wow. Go figure. I never would have seen that one.
You need to offer stronger evidence before I will even try to see it differently. all you say is Well Bret got booed. Big deal. That's a heels job. At least say why or what caused or his strong part in the booing other than he got on the mic. I mean out of his group, who else was going to get on the mic? Owen? He sucked. Bulldog? Boring. Neidhart? Can barely understand what he says anyways. Pillman? yeah, the loose cannon was gonna carry everything. Thing is that Bret could put together a complete sentence and was prety good on the mic. Not good enough to have done it without Stone Cold being the catalyst though. Oh, and btw, Dell Wilks sucks. The fued was already way over in popularity before they had him face off against Hart. They had already turned it into a USA versus Canada feud, which it wasn't at first.