It's not just France, but they are the lowest hanging fruit.
Beginning of a solution:
1. do not allow open borders with free movement of folks we cannot vet thoroughly prior to admission
2. encourage citizens to arm themselves (concealed carry, etc) for protection no matter location, etc.
3. acknowledge the enemy and be willing to do all possible to exterminate it
4.increase scrutiny regarding travel visas so as to not have so many illegals enter and remain using this path
5. follow closely those from USA traveling to and from Muslim areas where terrorism is prominent
6. work toward having the 'peaceful' muslim community do much more in the way of exposing those who may become radicals.
7. Insist that the US Constitution is supreme law and other US individual laws are to be followed to the exclusion of religious or others that might be desired by a particular sect or group.