WASHINGTON — The top U.S. commander in Afghanistan recommended on Tuesday that President Obama revise his plan and keep more than 1,000 U.S. troops in the country beyond 2016, just days after he said a deadly U.S. air strike mistakenly hit a hospital during fierce fighting in the north. Campbell said, however, that Afghanistan remains engaged in a violent battle against the Taliban, military operations in Pakistan have pushed fighters, including those linked to al Qaeda, into eastern and northern Afghanistan and the emergence of Islamic State fighters has further complicated the conflict. Campbell, the top commander of U.S.