Thankfully uncommon in North America. Growing up in Los Angeles where every bus has racks and every train car has bike spots, I was shocked the first time I visited SF and found I couldn't bring it on Muni trains.

I know DC bans them and Boston/NYC/Toronto have limited hours, but every other city with a metro seems to welcome them.

NYC subway allows bikes 24/7, only MNR and LIRR have time restrictions