Cold weather heat pump technology is consistently getting better, but I also think people underestimate how many heating days are above freezing even in cold areas and how much of the US and other places is mild enough in the winter for heat pumps to be fairly efficient nearly every day during the winter (especially if you look at population rather than land area).

If you look at a place like Minneapolis, which is normally considered a pretty cold US metro area, you do have a few months where the average temp is below zero. But you also have several more months where the temperature is cold enough to turn on the heat but well above freezing, where a heat pump is dramatically more efficient. When picking a heating system, it makes sense to consider comparative efficiency over the entire year, not just performance during the worst conditions in the middle of winter. Even in a city like Minneapolis, it's not obvious that heat pumps are less competitive over the entire year, even if their performance in January probably isn't fantastic.

I also think the practical geographic area extends further than people think. New York City definitely isn't the south, but per some random Googling, it doesn't appear to have any months where the average temperature is below freezing. Even Boston only has 2 months that barely drop below freezing. Most of the US northeast (definitely the mid-atlantic) by population arguably also falls into the range where heat pumps make sense.