Our cat travels quite well. He's not overly fond of sitting outside when we're camping (on a lead, obviously), but he really does enjoy being in the trailer and looking out the windows.
Before we leave the house, I'll put a harness on him with a tag with my cell phone number on it; the harness doesn't come off until we return home.
I just let him roam around the SUV while driving. I do put his litter box in the back of the SUV; unlike our dog, the cat isn't used to 'holding it' (and I haven't figured out how to get him to go before we get in the vehicle), so he'll generally be in there once or twice even on a two hour trip.
As mentioned already, if you're travelling to the US, make sure you have current rabies papers from your vet. I've never had a border guard give them more than a glance, but most state parks and some private parks give them a thorough going-over.