Yes, they can make the trip. I took mine from Alaska to New York - which was 10 days of driving and only 3 hotel stops. The most important thing is tempature. Since my trip was in the dead of winter and during an extreme cold spell - I kept them under 3 blankets with the heat on full blast ALL THE TIME. We're talking -40F temps for 1/2 of the trip. Sadly 20/24 died in the yukon due to an open window and my fish were under the damn window

. The survivors moved into my lap for the next 8 days. I had all my fish supplies within easy reach so I could do water changes at the hotels and I had a 2G storage container that i let them swim in for a bit in the hotel before putting them back into their cup.
If they can survive the alaska highway, they can take any road in the country - just keep the window shut.
This is what the survivors were in, and under like 5 flannel blankets.
Fish chillin in a hotel someplace in canada
Dog not happy to be sharing his mommy's lap with fish
did i mention that I also had a dog and chinchilla on this journey >.<
SInce your trip is from AZ to MD and its summer, I'm not sure heat packs would be a good idea.
I wasn't the driver but if you are doing the driving, I would put them into a cup - maybe a coffee cup with a lid so you dont have to worry about bags and getting fresh air. Secure the cup into a small cooler or something. I originally had petco cups taped into a cooler but since the number went from 24 to 4, i moved them into the little rodent carrier since I wasn't using it.