American society has polarized, it is true. Still, I believe only a tiny fringe minority will openly claim indifference to the WTC attacks because they haven't affected them personally. Much less show any support for the terrorists who committed these attacks.
At this point it's not even indifference, it's more like animosity between different regions and different segments of society. When was the last time anyone stormed the Knesset?
The US is home to 350,000,000 people. If you gather the craziest of these in one small place, you'll have enough force to storm a (poorly defended) Capitol.
The US always had various fringe, a-social and anti-social groups. Still, Americans do largely share a sense of identity, especially against a common external threat. To judge by some of the comments here, perhaps to a greater extent than Israeli society currently does.
