Detroit. I mean, really, how can you beat the Motor City for unfriendliness to bikes? You can't ride on the freeways (though why would you want to over there?), bike lanes are non-existant, except in far-flung suburbs like Ann Arbor, there is no real mass transit and what little exists is not geared for bikes.
Not to mention Michigan winters.
Then again, I moved away in 2000, so maybe something has changed since then?