Japan can bring every plane it posses to the US, by the time they’re ready to attack, the Western US will be more then able to repel the attack. Obviously if the Western US falls Japan will likely win the game, even without the 40 IPC NO bonus. What does Japan bring in that can beat potentially 32 Infantry, a mechanized infantry, an arty, 2 tanks, 8 fighters (12 when Anzac fighters lands), 3 tac bombers, and 3 bombers? This force averages over 20 kills on the defense.
Every strat I’ve seen that involves an attempt to take the US involves the US player blithely ignoring any invasion signs and making poor purchases. If the Japanese fleet moves toward the US, assume an invasion is coming, heck if they mass up in Seazone 6 on turn one, assume it’s coming. It’s silly not too, the US is the primary adversary for Japan, you cannot afford to chance it falling. Feel free to post your strat on how to successfully invade the Western US, I’m sure it’ll be picked apart. I really think that the San Fran rush was likely extensively tested, and it’s just not going to happen against any kind of decent player.