For this discussion, you're really torturing the definition of a bus if you're going to use BRT to mean busses. BRT does not meet most peoples definition of "city bus" as the conversation up to now has suggested.

I’m not saying BRT is better than light or heavy rail, but that should be a more common path for mass transit that is not utilized in the U

BRT would nearly always be a zero sum solution to make your statement true. You would have to subtract from current roads that accommodate traffic to create BRT to meet your metric. Land, espeically in dense cities is nearly always already allocated. If anything besides the zero sum BRT, light rail would likely be a better choice than BRT because it can subterranean or elevated with fewer building challenges/dangers.

I’m not saying BRT is better than light or heavy rail, but that should be a more common path for mass transit that is not utilized in the US

I'm interested in an example of a city you have a in mind that BRT would be a better choice than city busses or light rail.