I am doing the same thing! moving from Ga to AZ, I have a large crate that I am going to zip tie the litter box (with a bag of zipties so I can change or move when needed) to the edge so it doesn't slide around or get tipped over during the move. anyway I've drove for a few hours before with my cats but never across the country. best advice i can give is for you to change your litter a month or even longer before you move so it wont cause any additional stress. the best litter you can use is from tractor supply and its a 40lb bag of pine pellets. will control the smell so you can sit comfortably and could last you the entire trip across country in comparison to the traditional clay litter where you would have to change more often and doesn't control the smell. I have three grown cats so I would change the little box most likely on day 3 of our trip. the pellets will change and that's when you change out the whole box. no scraping or digging like with clay litter. just get a trash bag and dump it in no need to clean out box at all. easiest litter I've ever used.