The vastness of the land to be covered to communicate with one region with another.
There were limited methods of transportation in the 1700s and early 1800s. Once the trains laid their tracks, this problem no longer existed or it was reduced.
If you are interested, it is one of the reasons that the electoral college was developed. Georgia is many miles from Vermont and Maine.
The waterways by and large run north and south in the US. The might Mississippi is an example. The Missouri river in the north is very hard to travel even though it does go east and west.
