(Reuters) - U.S. President Barack Obama asked Congress on Wednesday to authorize military force against Islamic State that would bar any large-scale invasion by U.S. ground troops and limit operations to three years. Republicans, who control Congress, put up swift resistance to the proposal. They say Obama's foreign policy is too passive and want stronger measures against the militants, also known as ISIL. With Obama's fellow Democrats wary of another Middle East war, it could be difficult for the White House to win enough support to pass the bill, even though six months have passed since the military campaign began....