The best courses for "roots and traditional music from the United States", American folk music.
Blues Chords & Lessons: The Blues Guitar Of Broonzy & McGhee
by Jim Bruce
Blues Guitar Lessons - From Texas To Carolina
Smokin' Acoustic Blues Guitar by Jimmy Dillion
by Jimmy Dillon
Bluegrass Guitar Essentials: Webisodes 9 & 10
by Eric Beaty
Play Sonny Terry style on Harmonica and dazzle your friends!
by Ben Hewlett
Old-Time Banjo for the Absolute Beginner
by Anna E. Uptain
Learn to play tunes by ear on harmonica - no written music
Blues Guitar Lessons - Robert Johnson and Scrapper Blackwell
Acoustic Blues Guitar Lessons
by Daniele Pacchini
Instant Harmonica - play Dylan's Blowing in the Wind today!
Improv Bluegrass Theory works for Guitar Mandolin Fiddle etc
by Lesson Pros
Blues Rock Masters Inspired Series-Modern & Classic Volume 2
by David Taub
Blues Rock Masters Inspired Series-Modern & Classic Volume 4
Master the famous Eagles tune Take It Easy on HARMONICA now!