Coming to shanghai via cruise n after 72 hrs fly back to Los Angeles how I get visa

You don't need one.

Nice short answer there JD.... Absolutely correct. On my next visit to China after a big fail & being expelled from the country I worked out an itinerary that was 72 hrs 15 minutes.. I ran it past the Visa office & got a big NO! ...the 72 hours is calculated from the midnight following your arrival and not a minute longer. If you arrive at eg. 10 am you can stretch it out a bit... it worked for me.