Canadian-born journalist Robert MacNeil takes us on a three-hour tour of American vernacular, deep-rooted local dialects and rapidly evolving subcultural slang on “Do You Speak American?” (7 p.m., PBS).

MacNeil, the author of “The Story of English” (Viking, 1986), begins by taking a ferry from his native Nova Scotia to the coast of Maine, where some lobsterman fear that their old way of speaking (“ayah” for “yes”) may be dying.

Experts explain how the linguistic impact of the Revolutionary War was felt for centuries after the conflict ended. Residents of “Tory” cities occupied by British troops, including Boston, New York and Charleston, retained the English habit of dropping r’s. That accent can still be heard when a Bostonian turns “car” into “caah.” The same experts explain how proper New Yorkers, exemplified by President Franklin Roosevelt, also dropped their r’s — a habit that died after World War II. How and why is not explained.

MacNeil’s travels take him to coastal islands off South Carolina, where speech patterns from West Africa still endure. Pittsburgh has its own local patois, dating to its early Scots-Irish settlers. In fact, some Pittsburgh slang is identical to street-talk in Belfast, Northern Ireland.

Ever sober and respectful of every dialect and variation, MacNeil keeps the travelogue moving at a quick clip, taking in hip-hop slang, Internet and instant-messaging jargon, Appalachian mountain talk, unique Southern phrases, Cajun words, Spanish-influenced cowboy terminology, and “Spanglish,” the evolving hybrid of English and Spanish.

Tonight’s other highlights

• Scheduled on “60 Minutes” (7 p.m., CBS): the woman at the center of a Pentagon scandal; a medical disorder that threatens the Amish.
• Secrets from Claire’s past come to light on “Lost” (7 p.m., ABC).
• Doug and Carrie make new friends on “King of Queens” (8 p.m., CBS).
• CJ’s private life becomes grist for the Internet rumor mill on “The West Wing” (8 p.m., NBC).
• Sydney gets a new boss as “Alias” (8 p.m., ABC) returns with a two-hour season premiere.
• Interborough slayings baffle the team on “CSI: NY” (9 p.m., CBS).
• After the death of a tycoon, his wife and her lover become prime murder suspects on “Law & Order” (9 p.m., NBC)