Why C?

Thanks for your question @emanuel-centeno We're being asked to identify an assertion that would most support Kolchin's principle conclusion, so let's start by identifying what that conclusion is. We can find that beginning in line 40: "These differences in demographics partly explain differences in the kinds of resistance that slaves and serfs practiced in their respective countries." Answer choice C provides an instance where American slaves exhibited the kind of resistance that was more typical of Russian serfs, in cases where their demographics more closely looked like those of the Russian serfs. This lends support to the idea that slave and serf demographics influenced the way that they demonstrated resistance. Answer choice B neither supports nor discredits the conclusion: it tells us nothing about whether slave and serf demographics affected their methods of protest.

I didn't choose C because it said "Western Hemisphere" which could include many more countries then the US so it seemed to broad to me. Please explain.