Are you talking about the mail? There are some busy distribution centers around the country that are notorious for slow service, probably because of the volume of mail they handle every day. Chokepoints happen. The ones in California are in Bell (south) and Richmond (north).
I'm not sure exactly what you mean by "get through." I sense there may be a logical fallacy in there somehwere, but I may be wrong.
When I was a grad student doing freelance writing for extra money, I once had a check take 5 days to get from the publisher's office in Downtown Chicago to my apartment in Hyde Park — that meant traveling an average of 1 mile/day.
