Given that the greatest ever super-middleweight was British, the last undisputed heavyweight champion was British, the current linear champion at 140 is British, and there are numerous Brits in most Top 100 ATG lists, I think your statement is a bit unfair.
Aside from the Revolution of the 1770's and the War of 1812, Lennox Lewis could also be considered a Canadian where he started boxing and won the gold medal in 1988 and represented Canada at LA in '84. Looking at the early days of boxing, many of the champions were not born in the USA or on the 4th. of July. e.g. Paddy Ryan, Bob Fitzsimmonds, Jack Root, George Gardner, Joe Walcott, George Dixon and more.
You know Magoo, normally I think you're a sensible balanced poster but the above does not flatter you mate. I saw later posts
I just had to bust some balls for some shits and giggles mate. I need that every once and a while.....
Yes, I know he was born in East London, but he was Canadian in the Eighties when he finished his amateur days.