Long lines formed at international airports across the United States on Friday after U.S. Customs and Border Protection’s computer system broke down and dramatically slowed the processing of thousands of people arriving from abroad, including U.S. citizens. Officials say they would not stop processing passengers, but said they had to switch to a slower, alternative process. It was not immediately clear how long people were having to wait, but reports on Twitter showed clogged terminals and extremely long lines. “U.S.