Have any Americans served in the Canadian army?

A number of Americans served in the Canadian Army and Air Force in World War I, the Spanish Civil War and World War II. According to one estimate, in 1941, prior to the United State's entry into World War II, there were about 16,000 Americans serving in the Canadian Army.

American citizens primarily joined the Canadian Army during the World Wars due to the United State's reluctance to enter combat. American soldiers were generally sorted into Canadian units and fought alongside Canadian troops; however, one notable exception to this was the Eagle Squadrons, a World War I Canadian Air Force squadron made up entirely of volunteer American pilots.