美國洛杉磯有咩特產？

Nothing~

maybe you can buy a Dodgers' Cap. but u can find that anywhere. so , nothing special.
even Disney , Hollywood Studio products can be found anywhere in the world.
so, my answer : Nothing. i can't think of any.

I can think of:

Traffic jamAir pollutionGangsGraffiti
Seriously, nothing must buy. If you have to buy something, buy an "I Love LA" T-shirt or a fake academy award statue at any tourist shop. It will be made in China but it's something supposed to represent L.A.