logistics. neighboring states are sending stuff, but the us is 3000 miles wide. most states couldn't drive a firetruck to california in less than 3 days, and even then, there is a finite amount of water that can be pumped at once, or you lose pressure. they could use all the firefighters to cut firebreaks and stuff like that, and they can just hop plane and be there in a few hours, but equipment is another story.
United States