CHARLOTTE, N.C. — The nation's local leaders must press Congress and the Bush administration to improve the federal government's response to disasters before the lessons of Hurricane Katrina are forgotten, New Orleans Mayor Ray Nagin said Friday. "Everybody in this room should be concerned," Nagin told about 1,500 local officials at the annual meeting of the National League of Cities. "Everyone knows there's a certain amount of constipation in Washington. We need to be the Ex-Lax to bust through that." Nagin said he worries that the federal government's attention has been diverted less than four months after the hurricane. "Congress...