Which musical instruments originated in North America?

OK. I'm going to start the controversy. I reckon it's the sousaphone, that bass brass thing that you put on rather than carry. The required answer is probably the banjo, but that is a continuation of African instruments. The kazoo is a variant of the eunuch flute of European origin, and the mouth bow is world wide. Another possibility is the swannee whistle, but that might have European forebears. There again, there is the synthesiser...

I think he is looking for banjo, too.

John Phillip Sousa invented quite a few instruments and modifications for the purpose of facilitating marching with instruments, the sousaphone being the best known.

Many DJs in the world today use the record player as a rhythmic instrument - the phonograph having been invented by T. A. Edison in 1877, and is probably the only thing anyone uses as a musical instrument whose origins can be easily traced to the US.

There have been a total of THREE stringed musical instruments invented in the United States of America:

First, the 5-STRING banjo was invented by Joel Walker Sweeney in the 1800's. The slaves brought the 4-string banjar from Africa and Joel Walker Sweeney added the 5th string to create the modern 5-STRING banjo.

Second, John Dopyera invented the RESOPHONIC GUITAR in the early 20th century. The resophonic guitar was invented in order to have an acoustic guitar loud enough to be played with reed and "Big Band" instruments.

Third, David Ridge invented the BanaStar in 2011. The BanaStar is a fusion of three instruments:

5-string banjo (Ban)
bass (aS)
guitar (tar)

While not a physical fusion, the BanaStar combines fundamental and conceptual attributes of all three into an innovative new instrument. The BanaStar is the third ORIGINAL stringed instrument invented in the United States. The BanaStar is the ONLY stringed instrument invented in the US in the 21st century. (so far)

http://www.banastar.com

I am amazed that the electric guitar has not yet been mentioned! It was invented in the 1930s in the USA, and has been extremely popular...

See https://en.wikipedia.org/wiki/Electric_guitar

Let's not forget the dulcimer- http://www.oddmusic.com/gallery/om11400.html.

...or the Moog synthesiser: https://en.wikipedia.org/wiki/Moog_synthesizer

...or many of the weird instruments listed here (many of them American): http://www.oddmusic.com/gallery/

North America includes Canada, which gave us electro-pneumatic organs and the synchoros, among others:
https://www.casavant.ca/history/

... and Mexico, source of the rainstick https://www.watereducation.org/sites/main/files/file-attachments/rainstick_origins.pdf?1433872831

the jarana jarocha https://en.wikipedia.org/wiki/Jarana_jarocha and the arpa jarocha https://en.wikipedia.org/wiki/Arpa_jarocha

Thus it appears there has been far more than one instrument invented in North America.