Most of the world is applauding the thaw between the United States and Iran. Then there are the Arabs and Israelis. Their reaction is dread, and with good reason: neither trusts U.S. President Barack Obama to prevent Iran from acquiring a nuclear weapon or from at least acquiring the capability to produce one. Israel, which has a wide base of political support in the United States, will try to stymie any nuclear deal it sees as too lenient — but that won’t be easy, writes Elliott Abrams