So, the left has several solid solutions to deal with the problem of terrorism, both in the USA and Europe;
Complain about anything Trump does or says.
Import more individuals or their offspring from countries most likely to become ISIS sympathizers, or agents of.
Hand US (or Euro country) constitutional rights and citizenship to foreign citizens from hostile countries in the name of political correctness, and the continued globalization efforts. That way it's easy to claim that US, Brit or French citizen did the attack, because perception is important and over-glosses the reality that these terrorist attacks were done mostly by individuals with Middle-Eastern background.
Advise everyone to just live with it, and duck when it happens.