It's entirely probable.
One of Washington's greatest hopes, pre-revolution, was to be a colonel in the British regular army. While the situation for officers was different than that of soldiers, J.T. Flexnor in "George Washington, The Forge of Experience" (Little and Brown, Boston, 1965) states on p. 112 that, "Washington's heart was gladdened by a rumor that the Virginia Regiment was about to be incorporated into the British regular army."
It seems to me that there was a regiment of "Royal Americans" and perhaps a 60th Foot, raised in America. Were not Roger's Rangers part of the British army?
By extension, I think the Brits would enlist anybody who cared to join up.
Conversely, there were regiments of Canadians in the Continental Army and there were 50 Canadian voluntees in US service at the battle of Lundy's Lane in 1814.
James B. Ronan II
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