The United States and Saudi Arabia have arrived at a familiar moment in a love-hate relationship based on oil and cultural incompatibility. The two governments normally take a deep breath and decide that the benefits their strategic entanglement brings outweigh the problems it creates. But that stock-taking is not happening this time. Problems are proliferating instead of being quietly disarmed by adroit diplomacy. Washington and Riyadh are slipping toward new confrontations over the future of Iraq, democracy in the Middle East and U.S. objections to Saudi financing and support for Arab terrorist groups. These explosive issues already spin beyond the...