That those who are in favour of Napoleon on this board seem to be from the USA while those who are not are not usually British or ... Canadian ...
I am assuming this is because the USA was Boneys ally and French troop actions in Spain and response to guerilla actions would be seen as similar to there (sic) view on Indians ...

That goes a bit beyond "over-simplification".

When, where and how were the USA "Boney's ally"?

In the era, the American view of the Red Indians was that they (tribally) were all "uncivilized" except for the few who left the tribes to become "Christianized."

Meawhile all the people of Spain were Christian (although Papist) and therefore "civilized".

Therefore, your construct fails on the definition of a "civilized" people current at the time.

Christians were the civilized people, Jews were marginal, and all others were uncivilized - especially African slaves.