We have one North/South freeway, and 1 1/2 East West Freeways (I-94 is pretty short).
No, I don't carry any fuel cans. Even heading for Northwestern Montana, using State Route 3 to U.S. Hwy 12, to U.S. 191 to U.S. 87 to I-15 to U.S. 2, there is no shortage of all night gas stations/truck stops.
I usually start full, of course, then spend the night and fill up in Great Falls, top off in Shelby or Cut Bank, and that gets me to where I'm going.
Generally, I want to stop every 200 to 250 miles for fuel, regardless if I am in the truck or the motorhome. Rest stops are as needed.
I don't even carry fuel for the ATVs! A full tank in each is usually enough for all the traveling we do on them.