The issue is not the spirituality of what the Americans, or the zionists, do, but the practical political and legal implications.
They Arabs will be annoyed, but they are annoyed over a lot of things. Most object to Israeli presence in Jerusalem no more, and no less, than the Israeli presence in the rest of the country. To an Arab Muslim (and to a Jew, for that matter), there is really no differnce between Hevron, Jerusalem and Haifa – its all one country.
If the US moves the embassy, it does recognize that Israel has a right to at least the territory from the 1949-1967 borders, and that what is up for bargaining is what was conquered in 1967, and no more. It might force the Arabs to give up their bargaining position which has been “withdraw to the 1949-1967 lines, and then we’ll discuss what, if anything, you can keep of what’s left”.