My views are coloured by the fact that i live in the UK, where almost no houses have air conditioning.
How are heat pumps typically installed? Are they integrated into the radiator/hot water system? Or is some sort of forced air system setup installed?
I'd assume a mini split setup wouldn't be too uncommon. (Probably the cheapest route for most homes in the UK).
In the US the vast majority of homes and apartments are setup with forced air heating and cooling which really simplifies transition. I'd assume the UKs setup where everyone uses heated water to heat homes would make transition more expensive and costly.
Some new builds have mechanical ventilation heat recovery, which is a ventilation system with a heat exchanger. But I don't hear much about air to air heat pumps.
It's very possible I'm wrong in my perceptions here!
I'd assume that would cause a lot of issues if it is as chilled water would generate condensation (and the UK is nice and humid 24/7)
Europe has more hydronic/radiator mono-block heat pumps, with no refrigerant work needed in the field, which makes them easier to retrofit, assuming all the other plumbing is in place. Refrigerant work requires more training due to the high pressure and the potential for the high-GWP refrigerant.