The atomization of the citizens have had decades to fester in the US.

Single family houses, car dependent infrastructure, lack of private communications will all move people away from forming groups, and make it more difficult to organize.

Living in an apartment makes it easier to form a small group of common interests, you meet other people in similar situations, have ready access to private areas to discuss sensitive subjects, same goes for public transport.

Once a small group has been established, it is far easier to keep it going, than to establish a new group.

And once you have a group it is far easier to organize protests.