Because there's National Guard in every state. The National Guard deployed in LA is just the California National Guard. And it's just a fraction of the CA National Guard being used. And most of them aren't doing much (some are guarding federal buildings, most don't even have any orders), it's actually the LAPD that's handling the protests.
You can and should have protests in other cities but do so peacefully. If you spend too much time on lemmy you'll constantly be told we're about to storm the Bastille any day now. This place is full of psychos that are constantly pushing for violence. They are idiots, you should ignore them.
Honestly if I were conspiratorial minded I might think some of the violence was some false flag kinda shit because burning cars while waving Mexican flags is exactly the imagery Trump did all of this to get.