I am curious: do you happen to know where that was suggested? I don't remember seeing that suggestion before, and I should like to know where these French people are said to have come from, and when (other than Louisiana, of course, but that was a few tens of thousands of people, and later than the start of the US).

English speakers from various places in the British Isles, which had and have a variety of accents, came to North America, and accents changed further after that.

Mentioning previous answers is intended to provide quick pointers to existing answers, not to discourage further questions. AskHistorians welcomes follow-on questions, discussion, debate, and rebuttals.

There was a recent reply that had lots of links, under "Did Thomas Jefferson, James Madison, and other Founding Fathers from the south have what we now consider a southern accent?", https://www.reddit.com/r/AskHistorians/comments/7ypv5p/did_thomas_jefferson_james_madison_and_other/duiigvt/ , compilation by /u/tim_mcdaniel .

The first one, "How close was George Washington's accent to the modern American accent?", is not directly applicable to your question, but may be of interest if you care about linguistic details.