Well, if we go that way - I don't think many Americans can claim that they wouldn't fight in the ACW. Social pressure was enormous, and really, these men had no idea of how horrible war was. Plus, Americans tend to be 'patriotic'.
As for the Napoleonics - I dunno. Maybe I'd have 'fought' in the liberation war, but joining the army...meh. Might have gotten conscripted, though.