At about 5 a.m., loud banging on a front door quieted a chorus of crickets on a pine-ringed road in this Atlanta suburb. "Police! Policia! Open the door!" shouted the Immigration and Customs Enforcement officers. The raid, part of a new push to round up immigrants who have been ordered deported for criminal convictions or visa violations, was targeting a man from El Salvador who had repeatedly been busted on drunk driving charges. They came away instead with two brothers from Mexico, one of whom has the same name as the fugitive, who said they came illegally and will likely...