WASHINGTON—As the number of illegal border crossings increases, experts are warning that the sheer volume makes it easier for potential terrorists to slip through the cracks. An average of about 3,000 people were arrested every day in January after crossing the southern border illegally, according to the latest statistics from Customs and Border Protection (CBP). “I think the threat may very well be elevated and escalating,” said Todd Bensman, senior fellow at the Center for Immigration Studies and author of “America’s Covert Border War.” “I believe that we are at the front end of another mass migration crisis on our southern border.” Bensman said attention should be focused on the current changes being made to the U.S. asylum system and any subsequent gaps that are created. “We should remember, most of the terrorists that infiltrated the European borders abused that asylum system—made up fake names and fake stories—and got in …