I sat in a car for 8 hours each way at 36 weeks, it was so uncomfortable. Asked my midwife about doing it again a week or so later, she said it could trigger powerful braxton hicks and start labor, which I already felt on the way home at 36 weeks. These drives were because of my father-in-law dying, so I ofc wanted to go. Glad I took the first drive so I could say goodbye. By the time of the memorial I had already given birth at 38 weeks, and we considered driving with a newborn, but decided along with a pediatrician in the NICU that we stayed there, so my husband knew we were taken care of.
I digress, but do whatever you're comfortable with, and hopefully there are hospitals along the way :)

It depends on your general condition. I have travelled when I was 37/38 weeks pregnant 6,5hours. You can check it with your obstetritian