I can only laugh at the notion that the United States hasn't done enough about ISIS, or that doing more in Syria and Iraq would make us safer at home. ISIS as a "state" has only lost ground since the US began its operations against them and their organization has essentially nowhere to go but down in the long term (even though taking important holdings like Mosul from them will still be a long and difficult task). But, ultimately, there is no realistic domestic political solution on the horizon for the regions they inhabit, and furthermore none would be created by injecting 100,000+ US ground troops. As "permanent ground troops" is the only prescription that the right will offer which the US is not already pursuing, I have no regard for any criticism that the right will make on the issue.
Meanwhile, we cannot stop every manipulable nutjob in the world who might do something terrible in the name of ISIS. The only way you could begin to address that would require a totalitarian approach that would still fail to guarantee 100% safety and would harm society far more than anything like San Bernardino. I say this as someone whose mother is a county government worker in California, whose workplace was put on lockdown the day after San Bernardino happened due to a gun sighting. Living in fear and buying into hysteria accomplishes nothing.