So reads an AP headline — the Washington Post headline is nearly the same. But, as Best of the Web points out, here's an important fact from the text of the AP article, also reported in the Washington Post piece:
The United States and other leading cluster bomb makers — Russia, China, Israel, India and Pakistan — boycotted the talks, emphasized they would not sign the treaty and publicly shrugged off its value. All defended the overriding military value of cluster bombs, which carpet a battlefield with dozens to hundreds of explosions.
Why then "111 nations, but not U.S."? I take it "111 nations" was meant to suggest some broad consensus, and 111 is more than half the number of sovereign states (though I wonder what fraction of readers will have a relatively accurate sense of that). But the presence of such a consensus doesn't seem a terribly accurate implication, it seems to me, if indeed the three most populous countries and seven of the ten most populous countries have declined to sign. (Bangladesh and Brazil seem not to have signed, alongside China, India, the U.S., Pakistan, and Russia.)
Perhaps more importantly, comparing this list of the countries with the largest armed forces and this list of signatories reveals that the 13 countries with the largest military forces have all declined to sign the convention — an even starker picture than that painted by the AP's story text. That many nations with tiny militaries pledge not to use a certain kind of munition doesn't mean that much, it seems to me. That the 13 largest military powers decline to so pledge strikes me as meaning a lot more.
It sounds like it would be accurate to say that "most western Democracies, but not US, support cluster bomb treaty." It would also be accurate to say that "most countries, but not most of the largest military powers, adopt cluster bomb treaty." And given space constraints, it would be accurate to say "Nations Split on Cluster Bomb Treaty." But the implication of the "111 Nations, But Not US" headline strikes me as pretty misleading.
Note that the lists I cite are from Wikipedia; I'd be glad to see more authoritative lists if you can point me to them, and to note any errors in the data I've gleaned, if there are such errors.