It isn't too hard to figure out the target audience for this list, you're right about that. Casual American gamers who probably only played (or bought) 1-3 things from that list, tops.
Disclaimer: All quotes below are from the purported point of view of GameTrailers and are not my actual opinion or arguments.
Think putting the 3DO or Jaguar on the list was bad? Consider yourselves lucky. GameTrailers could have just as easily put the Turbografx/Duo on there and rationalized it by bringing up the lame advertising, 2-button controllers, the NEC/TTI market share versus Sega & Nintendo or any number of "facts" that "prove" it "sucked." They'll say who cares what it did overseas because this list is primarily for gamers in the US. When it boils down to it, GameTrailers could have also come up with a few reasons to include the Sega Master System or even the 7800 because they "got their butt kicked by the NES in America" (that would be their words, not mine). They would say "Who cares what SMS did in Brazil or some other countries nobody has ever heard of? This list is being read in the US."
Hell, if you're a site like GameTrailers, the reality is you can put nearly any game system (not computer) except for the 2600, NES, Game Boy, Super NES, Genesis, PS1, PS2, XBox, etc. (insert one or two big sellers I may have missed) onto a list such as this and come up with at least one or two arguments even if those arguments are shaky at best. It will get a lot of hits, generate tons of traffic, get people talking on message boards and presumably have some positive impact from an advertising standpoint.