How much of this is because because emission standards in the US reward heavier vehicles, and vehicles over 3.5t get tax benefits and skew the market in the opposite direction than in most (all?) other countries?
Not much when the big trucks outsell the small luxury cars. The most I could get a bmw m3 configured for was $86000, it wasn't hard to get a f150 over $100k.
If money mattered you can look at the toyota corolla for much less than the cheapest f150.
Enthusiasts want small trucks. Americans don't want small trucks. They don't want a single-cab S10. They wouldn't even want a double cab S10. What they actually want is a minivan but they're too far into not-cool territory to be a consideration so they look to the mid/full-size SUV and/or truck segment. It is true that you can't really make a small truck in the US any more, and that automakers do like it that way, but it wouldn't change anything even if you changed the CAFE requirements.
As I said, they already cost more than smaller and cheaper alternatives. But people buy them anyway.
Heavily vehicles may be cheaper for whatever reason you cite. But they are still much more expensive than smaller sedans. People still buy the heavier vehicles.
It's not 3.5 tons, it's the footprint (track width * wheelbase).
The emissions standards reward larger vehicles that generally start around $35k-$40k. Americans just love going immediately underwater on a $100k Grand Wagoneer.
