Despite his evocation of a world seemingly abandoned by God, McCarthy’s stance on religion is never clear. However, he consistently employs the language of religion and a Biblical style.
Exactly which coast the road has led to is unclear, but it is likely to be either the Atlantic coast of Georgia or South Carolina, or the Gulf coast of Florida.
If it's the Gulf coast, then a likely candidate for this "murky shape" is Panama City.
The word "hagmoss" seems to be an invention. This is probably Spanish-moss (also called graybeard), which is not a true moss but an epiphytic plant.