Miami Herald: Mexican President Felipe Calderon's appearance Thursday before a joint session of Congress dramatically illustrated - and possibly reinforced - the partisan divide that's stymied progress on immigration legislation. In his 40-minute address, Calderon sharply criticized Arizona's tough new immigration law and the United States' refusal to ban assault weapons, which are being used in the violent drug-gang shootouts in Mexico. Afterward, Sen. John Cornyn, R-Texas, said Calderon "crossed a line" by urging changes in gun policy, and Sen. John McCain, R-Ariz., who's become a hard-liner on curbing illegal immigration, declared, "I've never heard of another country's president coming here and criticizing the United States like that."