If the Americans generally agree with what is being said, and have voiced the same sentiments themselves, then vetoing this will look very very bad. After all, the US has recently seen very little return on its investments in and support for Israel. It could even be argued that damage has been dealt to American interests by Israel's continuing resistance. With governments representing hundreds of millions of people around the world recognising Palestinian statehood and borders based on the 67' armistice lines, the Americans will be isolated. What's more, I doubt that a veto will grant them much leverage with Israel in regards to restarting the peace talks. This then begs the question: why would the American administration continue with this flawed approach?
U.S. sanctions Russia's state-owned arms exporter Rosoboronexport (Reuters)
from the article: Arab nations submit draft UN resolution condemning Israeli settlements