Hi, again. Indeed, there was that greater death toll. But this somewhat tongue-in-cheek article is specifically about the impact of American death tolls on American memories of their presidents. You're right, though, that if a president has many non-Americans killed in an unjust war, that too should reflect badly on him.
I doubt much of any population that would allow such a war to happen would care nearly as much about the deaths of foreigners as about the deaths of their soldiers. Any country that would find foreign and domestic casualties equally intolerable wouldn't have built such a war machine in the first place or they'd prevent the unjust war from happening.