Kross: Yes and No, (in addition to the U.N. details already given) while Washington DC & all the other midwest farmer's field-based missile silo military installations were badly gouged from the Earth by direct hits in the initial nuclear devastation, San Francisco was the "Wolf 359" of WW3 & The Eugenics Wars.
Survivors were cut-off from going North to Canada during Khan & The Supermen's overthrow of Socialist Countries like the U.S. due to the Eugenics War and the Hermosa Quake in 2047 that sank much of Southern California, The Queen Charlotte Islands & other northern outlying islands. (Vancouver Island, Quadra, Cortez, Seattle's Mercer Island, et al.)
They either sank under 200 feet of water or disappeared altogether along the Juan De Fuca Tectonic Plate, compounded by nuclear assaults on shut-down, past or current American/Canadian Forces Bases in the area (ie: CFB Comox, Weapons Testing Range @ Nanoose Bay).
San Francisco became the economic fallback position (see the large fleet yards already mentioned,) for the civilian populace, conscientious objectors, etc. in the event all else failed.
The American People of San Francisco succeeded in somehow gaining the political and personal confidance of the remaining global populace by showing them ways to face "Turn The Other Cheek", ways to incorporate non-violence into day to day life. Extra-terrestrial intervention (protein resequencers, deuterium farming, holodecks, the ability to leave Earth to find a Humans-First (see "Terra Prime") "Holy Land" where they'd never be bothered by those who aren't up to their standards, and other alternatives,) did the rest.
The stubborn religious zealot-hardliners that couldn't stop themselves from (gaybashing, burning crosses on African American's lawns, etc.) were wiped out in the fighting in the meantime, urban deterioration such as the L.A. Riots, vaporized in the initial attacks, died from radiation sickness, substance abuse, personally self-destructive behaviour such as drinking and driving, contracted AIDS / STD's in a time when medical help was back-alley for even the most priviledged survivor, or commited suicide from overwhelming distress during the Sanctuary District era. Or were wiped out during The Romulan War, Tzinkethi War, Klingon War, etc.