The reality is that the UK position is really our position and most of the world's. Congress has passed various laws and resolutions on the status of Jerusalem essentially alligning our position with that of Israel. However, Clinton and Bush 43 have either received waviers or ignored the requirement for the US Embassy to move to Jerusalem. The reality is that Congress makes these laws and resolutions for domestic consumption but give a wink and a nod when it comes to taking any concrete action.
If the US were to unilaterally move our Embassy to Jerusalem and recoginze Israeli sovereignity over an undivided city, it would essentially end our role in any future peace negotiations and inflame the Arab world even further against us. Currently, virtually every country with diplomatic relations with Israel has its Embassy in Tel Aviv or its environs. I predict that Obama will delay any move to Jerusalem of the US Embassy just like Clinton and Bush did.