You must submit your passport either in-person or mail it to the LA VAC. You cannot mail it directly to the LA visa office.In the US, in San francisco. So if we can send the passports via the Canadian Visa Application Center in Los Angeles: https://www.csc-cvac.com/. or directly to the CIC office in LA it would be great.
Here's how to do it:
http://www.csc-cvac.com/en-US/selfservice/cvac_application_processing