Well, I am coming from the netherlands ;) San Francisco and New York are definitely nice cycling cities from what I've heard (and also don't have many of the other issues I listed). However, I was under the (perhaps wrong) impression that in a substantial area of the US, drivers are either inattentive of or actively against cyclists? But probably only the bad news gets out.
You seem quite knowledgeable about these issues. If you have time, I'd love to get your perspective and advice about U.S. cities (though this might not be the appropriate place, I put my email in my profile in case you have time).
Then like I said, with that standard, everywhere else is bicycle unfriendly. :(
An email is coming, but I think that one of the big things (and San Francisco has this badly) is that the US is has been so car focused for so long that it is not exactly something that easily changes. But, compared to what it used to be, I think it has changed and still is changing.
I don't think it is unique to USA. When I was in London in the late 90s, I was told "You want to ride a bike? You'll get killed!" Now there are bike lanes and bike share programs and all sorts of things, and while there are still places to avoid and even back in the day there were bike-able places, it's gotten much better.
You seem quite knowledgeable about these issues. If you have time, I'd love to get your perspective and advice about U.S. cities (though this might not be the appropriate place, I put my email in my profile in case you have time).