I've lived all around the US, and don't think I've ever lived anywhere with central air. Well, that's not quite true: in New Mexico I had a roof mounted swamp cooler, but that's evaporative cooling and not a heat pump. Elsewhere I've occasionally had and used a portable compressor unit, but rarely. I hadn't realized air conditioning was so overwhelmingly prevalent. Based on people I know and associate with, I would have guessed less than half that rate.