Yes all terrorists and anyone else violent should leave the USA. They won't though, because the rich don't want to pay for someone else's security. The rich dwell in gated communities with guards at the gate to keep the hoi polloi out. The rich have chauffeur bodyguards to drive them and keep them safe. The rich don't want to fund security for the non rich, and the non rich can't afford enough police, private security, and prisons to get the job done well. The murder clearance rate is only 50% in some cities. Think about that. Half of all murder cases in some cities are never solved. Some of the people charged are not even the right people. Years later new DNA evidence or some such proves the wrong person spent years in prison while the real murderer still walks the streets.
America is not a rich country. 5% are rich. The majority are just getting by. The bottom 50% are barely getting by. No way can the bottom 50% afford excellent security in their poor neighborhoods. Terrorists can hide there with relative ease. The top 10% richest in the USA last 20 years longer than the poorest 10%, on average.
There are 2 different Americas. One for the rich, and another for the majority. The majority can't afford to locate and deport terrorists from their neighborhoods. The bottom 50% can barely keep food on their tables, let alone have anything at all left over to hire security forces to hunt down terrorists.