Dimensional lumber, gypsum board, plumbing pipe, and electrical conductors are commodities. Heat pumps are not.

There’s no need to subsidize commodity items, there’s plenty of competition to keep prices reasonable barring any massive supply/demand shifts.

Can't speak to the rest, but lumber has had significant import tariffs to the US for decades. So it doesn't seem as if relative affordability of that commodity is an issue (at least for the last four decades).

https://en.wikipedia.org/wiki/Canada%E2%80%93United_States_s...