Look, there are enclaves of racist whites all over the USA, you wouldn't want to live in those places but where you are going will be full of tourists of all colors and orientations and large percentages of the local population will be people of color, as mentioned before mostly Latino. We've done similar road trips through those areas, more than once on DH's Harley. You'll barely register on the local radar, as said, your Brit accent will excite more interest than your color. Bikers do tend to be mostly white, but the ones you're likely to meet at a tourist road motel in Arizona or Nevada will be liberal, middle-aged, middle class roadtrippers from California like me and DH rather than hardened Hell's Angels.
As for truckers, a more diverse bunch you're less likely to meet, they drive thousands of miles across and back through all the states and a freight driver you meet at a motel in Arizona is more likely to actually live in Chicago, New York, Los Angeles i.e. hundreds and thousands of miles away where the local demographic is much more diverse. Honestly, the freight companies here can't afford to be picking and choosing only white drivers, they're begging for drivers, it's a hard, tedious, heavy job involving days and weeks on the road and driver turnover is high because so many can't hack it, if you can pass the heavy goods test and a drug test it's "here's the keys, hit the road".
Driving here is a doddle compared to the UK, if I can drive there you can drive here. The roads are wide and well-marked, plenty of rest stops along the way, especially out on those vast desert highways where you're going. Get a good GPS (sat nav), set the cruise control for those long, long stretches of empty road and off you go.