The US veto will underline the pressing need for reforming the Security Council. There is a growing opinion that the SC does not reflect current world realities (which of course it does not), but reforms have been held up because there is no consensus on what needs to be done. India, Brazil, Japan, and Turkey want permanent seats, and the US is resisting these demands. A US veto at this point, specially one which flies in the face of a bedrock principle of the UN, would certainly lead to increased pressures to reform the SC, which in turn would work against US interests.
Hungary's Orban: Refugees threaten Europe's Christian roots (Reuters)
from the article: Abbas rejects U.S. request to withdraw UN settlement resolution