I think the problem is US federal emissions law. Toyota probably doesn’t want to incur the development costs to offer these vehicles in the US as their other SUVs and pickup trucks sell very well here. I see many Tacoma’s, Tundras’s, 4Runners etc. I don’t know whether there is any option for modifying a new Toyota diesel safari vehicle to meet US emissions, even privately. You can however bring in 25 year old vehicles under an exemption. There are several boutique operators who buy these vehicles in Japan for import to the US (all RHD of course).
I’d love a 79 series Toyota pickup truck, 4.5 liter diesel, manual transmission, lots of purpose built lights, canvas, 14 ply tires and 180 liter dual fuel tanks. That would be the sweetest ride imaginable and perfect for the Big Bend country with its narrow rocky roads. I shredded a 10 ply tire on my pickup truck on a trip there to look at a property (which I was unable to find).