By Ted Hesson and Kristina Cooke WASHINGTON (Reuters) -U.S. President Joe Biden’s move this week to block migrants at the U.S.-Mexico border aims to reduce record crossings and shield him from Republican criticism but is a turn away from his campaign promise to restore access to asylum. Initial backlash to Biden’s policy shift also signals it could be challenged in court, from both those who favor restricting immigration and advocates for asylum seekers. The Democratic president on Thursday announced a new two-pronged strategy that pairs deterrence measures blocking Cuban, Haitian and Nicaragu…