I NEVER thought I would be defending Canadians, after years on the radio along the New York/CANADIAN border and having Canadians always call to request bands from their country.
It was such fun taunting them over the airwaves 
BUT.....Canada HAS actually had the last laugh on America. At this point, Canadian radio is SOOOOO much better than its U.S. counterpart. you can hear amazing music up in Canada, especially classic rock and obscure-to-Americans tracks.
As a Canadian from the single largest (though, to be fair as regards your later argument) most diverse radio market, I have no idea what you're talking about. Top 40 is top 40 all across the continent.
The only good thing that we've had happen in radio up here recently is that a University radio station (1 of 3 in Toronto) went under. There was stiff competition for the rights to that point on the dial and luckily the regulator decided to not let major players in the market even bid. It was billed as an all new independent music station. We were all skeptical, and with good reason. Though it does play some indie music (usually bands that were just signed to majors or are well on their way vs actual indie music) it's mostly playing retro 80s-90s alternative rock, basically like good olde CKNY's playlists in their heyday (now Edge 102, playing horrible "emo" and _core type shit... some neumetal too), which is hilarious, but I'll take it because I don't like it when I hear The Clash on the 'classic rock' station; makes me feel old
).
Anyway, back to the arg - Rap didn't kill rock (though I understand that arg considering how that's pretty much what teen white boys were listening to almost exclusively until very recently). These things come in waves, and rock is coming back (even with the black kids). (Mainstream/,ajor label) Rock got lame; irrelevant and derivative self-parody - for about 5-10 years there I didn't hear a single good new rock song on the radio. Now that rap has run it's coarse and done pretty much the same thing (from OG MCs to silver spooners to top 40 internet meme jokes) kids are flocking back, why, because rock is fresh, or at least relevant, again (though now it may be called other things, if there's a distorted guitar on nearly every song on your record you are some subtype of rock).
On the indie side, it never went anywhere and was always relevant, but since the echo boomers weren't in college yet this is always ignored (underage, can't get into the clubs, find out about the bands). Now they are (at least some of them) and lo and behold look what's happening and the rest are seeking the stuff out on the internet, and hitting paydirt.
It's not resuscitated yet, but far from dead. Stable and in recovery. It's Rap I'd be worried about now.... though I seem inclined to think it'll come around again too. They can't control or destroy these mediums of expression/forces for socio-political change, all they can do is slowly corrupt/co-opt them into banal irrelevance when they hit that critical mass of popularity.
