The California National Guard is a branch of the domestic United States Army. Its sole duty is to protect the American state of California on the American West Coast. It's not mentioned or even shown, but it's possible that since California was the next last state on the west coast, they sent reinforcements and troops up to Washington State.
Much like the other states, California has its own National Guard force to protect the state from foreign and domestic invasions. During World War IIIs breakout in Europe, many of the U.S. National Guard forces were probably sent to assist in the defense of Western Europe from the Soviet offensive. California, being a big state, must have had at least four battalions worth of army units and only a couple were sent off to Europe. When the Sovets invaded Washington (State), California National Guard forces went on high alert to a possible chance that the Soviets would move out of the state quickly and move through Oregon to the state of California.
Although it's unknown how well-prepared they were for the invasion, California National Guard didn't have to even worry as the Soviets didn't make it far anyways. Most likely, the U.S. Pacific Fleet was more concentrated near California and that is probably why the Soviets didn't invade California. After the Battle of Pine Valley had stopped a southern advance down the West Coast, the California National Guard could only send a few units up to Washington to help the Washington National Guard fight off the Soviet invasion. California and the other states were finally safe for the time being after the Soviet invasion was defeated at Second Battle of Seattle.