I don’t know if unprecedented is the right word. But after Carter, a noted non-friend of Israel, the US has vetoed any UNSC resolution that claimed that Israel holding Jerusalem was an illegal “settlement” and had to be given back.
The reason is that not all settlements are created equal and while the US is against settlement activity that would severly limit the contiguity of a potential Palestinian state, Obama has prior to this always aknowledged that Jerusalem and the main settlement blocks would remain in Israel as part of “land swaps.” Meaning that Israel would give the Palestinians other land in exchange for the settlements.
By treating all building/occupation post-1967 equally, this resolution decreases the chances of peace. Israel is never going to give back Yerushaliym and if they will be censured for that anyway, what do they have to benefit from giving back anything. This resolution makes Israel’s last, best offer illegal under International Law. So why would Israel respect or abide by International Law?