I think the Federal Government should do a lot, but there are lines I don't think the Government should cross. So, based on how you worded your question, "ALL IT CAN" I have to answer no.
The Federal Government could, for example, have gone on a mission to confiscate all mechanical weapons from all Americans because She MIGHT use them in an attack. They could have gone door to door and searched all buildings for weapons to confiscate.
They could have insisted on psychological examinations of all people inside the United States and eliminated anyone who illustrated any tendency toward violence.
They could have restricted any and all travel.
They could have inserted listening devices in everyone homes and places of business and set a computer to pick out code words that warned imprisoning those who uttered such words.
There are a lot of things that might have resulted in a reduced likelihood of the California attacks from happening that I would be against the Government attempting.