By David Morgan WASHINGTON (Reuters) -U.S. Senate Republicans on Thursday blocked debate on a bill that represented the first effort by Congress to address mass shootings since a white supremacist’s killing of 10 Black people in New York and a gunman’s massacre of 19 pupils and two teachers in Texas. The 47-47 vote along strict party lines fell short of the 60 yes votes required to launch debate in the 100-member Senate on a bill titled the Domestic Terrorism Prevention Act. The vote effectively blocked the bill which would have authorized federal agencies to monitor and report jointly on dome…