Maybe not, but it's possible many post offices would need electrical supply upgrades to handle having their entire fleet plugged in all at once. Not impossible or even difficult, but not free either.

I would assume they're already in half the parking lots in the North - block heaters would require outlets, so anywhere that gets below -20C would likely be able to have electric vehicles today.

Block heaters are only needed for diesel vehicles or areas with really low temperatures. I live in Michigan and the only block heaters I know of are used for school buses.

I guess I'm wrong. I assumed they'd be more common, given how everyone I know has one in southern Alberta (Canada). I thought America would be similar in areas to the North. Granted, -40 (which it gets to here) does count as really low.