Maybe, but frankly, a lot of bigger names were left off...
Dante, for one...Milton...the Bronte Sisters (though no real shock there and, again, not a huge fan myself)...Toni Morrison, Langston Hughes, Richard Wright or any black writer (unless I'm missing someone?)...H.G. Wells, a bit shocking for our sci-fi-happy crowd...
Though honestly, the omission I'm most shocked at is Ernest Hemingway.
I'd have thought he'd be a lock to get in, not only one of the best-loved American authors, you could argue that he's one of if not the most well-known and respected American author on the world stage.
Twain and Poe are also pretty famous overseas, but Hemingway just crosses boundaries--he even cracked Le Monde's 100 Books of the Century list, something not many American writers did (and two others that did--Steinbeck and Fitzgerald--are also missing from the list.)