It is, but the number of options, configurations, engine choices, etc are fairly limited compared to the rest of the world. For example, the rest of the world was able to enjoy the 4-door crew cab version, but that model didn’t appear in North America until a few years ago.
I believe Toyota can market a 3500/ F350 competitor with a minimum of alterations.
Tale the long bed of the Regular Cab and graft it to the CrewMax Cab, on an appropriately lengthened frame. Bolt on some plastic/fiberglass fenders on the back for a dually.
Something like…THIS!