By Ted Hesson, Susan Heavey and David ShepardsonWASHINGTON, March 3 (Reuters) - U.S. Homeland Security Secretary Kristi Noem during congressional testimony on Tuesday stood by her remarks calling the acts of two U.S. citizens shot dead by federal immigration officers in Minneapolis "domestic terrorism."Noem, who is overseeing Republican President Donald Trump's immigration crackdown, was pressed about her statements by Democrats and some Republicansduring a Senate Judiciary Committee hearing.