You have to understand the cultural context translated between countries.

When the french protest and riot and burn shit, that is the French cultural language of protest, a thinly veiled threat that the state is only in charge as long as the public gives it a mandate. If push comes to shove, the public can always find a new state to run things. They evoke the spirit of the French Revolution as a core message. It says "we did it last time, and if you force us, we'll do it again."

Translating this to the American context, when the government became so corrupt that a Pedophile and convicted serial rapist and fraudster and his band of merry fascists and techno-trillionaires threaten the very foundation of American society, Americans do what they are culturally programed to do. They shoot up a school full of innocent children because deep down they know their culture has no future worth living and it should end out of mercy for future generations. It says "We are cowards for allowing this monstrosity to exist and it doesn't deserve to be experienced by anyone.".

Understood in this light, they have been protesting for years and years with escalating ferocity.

Edit: spelling and clarity