Previous U.S. presidents of both parties, as well as nearly every other country, refrained from opening embassies in Jerusalem, arguing that the city's final status should first be resolved through Israeli-Palestinian negotiations.
What's not mentioned any more is that the President said in his announcement, and since then, that the final status of the city of Jerusalem would be resolved through the peace process by parties in the region. So moving our capitol does not decide this.
Israel's capitol--and our embassy-- are in West Jerusalem, not "Jerusalem". East Jerusalem remains under Palestinian control with the dimming hopes of it being the capitol of the state of Palestine.