I don't think it was so much 'America wasn't ready for it'...

so much as it was that the show was just not 'hit' material.

I think I can recall MAYBE three cliffhangers total during all of the five seasons.

Most of the time the episodes just end. Sometimes on a very indifferent note.

There was nothing exciting about the show unless you just stuck with it.

Oh and there was no focal character. McNulty was kind of the main character, but not at all in Season 4, and by himself he wasn't enough to carry the show. The ensemble was the best part but hell, they changed the focus so much that there wasn't much to build a following around. I mean I loved that damn show but I just can't picture Bunk, Daniels or Herc becoming the next superstars on the cover of Life magazine.

No cliffhangers. No 'pretty' stars. A take-it-or-leave-it storyline that got so tightly woven that by season 3 they practically never even had to resort to scenes with random titties thrown in (which they did plenty in season 1).

This became one of my favorite shows but honestly I'm surprised it lasted five seasons. Hell I kind of think the creators of the show were surprised it lasted so long. The first few seasons all end as if another season was uncertain.