This is not about Quebec or Acadia, but this is where my North American French stuff goes, so: in reading a book on Prince Edward Island French,
King, Ruth. 2000. The Lexical Basis of Grammatical Borrowing: A Prince Edward Island French Case Study . Amsterdam: John Benjamins.—I've come across a mention of Frenchville, PA, settled in the 1840s, which appears to have retained a distinct dialect of French into the 1960s.
As Ruth King says, there have been no studies on it apart from a glancing mention in a 1973 dialect survey; and Wikipedia does not even know Frenchville exists (it's now part of Covington Township, Clearfield County).
At any rate, I've now added a paragraph on Frenchville to Wikipedia's French language in the United States article. Frank Merat, an Electrical Engineering professor from Frenchville, has the most material online on the village. And I haven't sighted Haden's 1973 survey, although I don't think it'd say all that much.
I assume it's safe to go to Frenchville without a shotgun nowadays...