BAGHDAD (AP) — A suicide car bomber struck a U.S. patrol in northern Iraq on Monday, killing four American soldiers and an Iraqi interpreter in the deadliest single attack against U.S. forces in nine months. The blast occurred as U.S. vehicles were passing near an Iraqi police checkpoint in Mosul, Iraq’s third largest city and the last major urban battleground in the war against al-Qaida and other Sunni insurgents. American casualties have fallen to some of their lowest levels of the war since thousands of Sunnis abandoned the insurgency.