Autotrader says there are 246,000 used trucks for sale nationwide with AWD/4WD and 38,000 with rear wheel drive. For new it’s 429,000 AWD/4WD vs 51,000 for rear wheel.

Volume wise it’s of course Texas with Wyoming, Montana, and North Dakota having the largest ownership share.

The majority in that statistic are selectable 4WD, which isn't the same as AWD. Pushing the two groups together skews the numbers a bit. Most trucks since the 1970s have been 4WD, ever since companies like Muncie and Borg-Warner started selling axles to Ford and their cohorts. AWD trucks are a relatively new phenomenon, with the first one I can think of being the limited production GMC Syclone in 1989, and it being a truck was an emissions loophole. I think the 2005 Honda Ridgeline was the first real mass produced AWD truck, or perhaps the Subaru Baja from 2003 if you consider that a truck rather than an open deck car. Right now I think only the Ridgeline, Hyundai Santa Cruz, and Ford Maverick are sold as AWD, whereas every other truck is selectable 4WD.