one of the issues was they timing that you speak of. MTV in the 90s was all "new country" commercial pop and rock and not a lot of service was paid to the niche groups.
other than that, there is no real concept of national radio in the US. Unlike all the BBC1/essential mix types, that did not exist in the US during the 80s and 90s and mostly doesn't now outside of internet radio, which is so fragmented.
radio is local market only and if you want to know how it really works, read "Hit Men: Power Brokers & Fast Money Inside the Music Business". it is actually a great read but shows how corrupt us radio was.
that which we listen to did not have the money to compete with the major labels that pushed product at the time in the local markets.
But Aural does have a point in that New York, Detroit, Chicago, Miami, Boston, LA and San Francisco all had great scenes, but they centered around the cities and it was not a national thing.