Reddit reviews The Lost Colony of the Confederacy (Volume 69) (Williams-Ford Texas A&M University Military History Series)

Here is a citation from Guy Bailey, and here's a book about "The Lost Colony of the Confederacy."

The lack of dialects in colonies is due to two factors - lack of time and homogenization. In England, there have been hundreds of years for different groups to live apart and have their varieties of English develop separately. Consider that until the Louisiana Purchase of 1803, most of the United States lived on the Eastern coast, which is where the most diverse dialects of the United States are. The cities and towns on the Eastern coast had more time to develop differently compared to the Midwest and Western states. They also had more time to be "isolated" from each other, in an era where communication and movement between cities was much more difficult. That's the reason that Western dialects are more homogenous - there's a lot of movement, resulting in leveling of dialect differences, and just not enough time. But that doesn't mean there will never be new dialects. There are already sound shifts that can be found in California that aren't in the rest of the west, for example.

Although I'm not familiar with dialects of other colonial/colonizing languages, e.g. Spanish, French, I would wager that something similar is probably happening there. Although at least with Spanish, the different Spanish countries have noticeably distinct accents, mostly with regards to lexicon and intonation. Perhaps because those countries had been settled by the colonizing force longer than the American West? And I cannot say much on the topic of French.