Certainly. Remember, only two months before, Pearl Harbour, several thousand miles from Japan, had gotten a royal pasting from Japanese aircraft. The first Japanese carrier wouldn't be sunk until May '42 (Shoho, a light carrier). So given that Japan still had all the carrier forces which had pasted Hawai'i, it was entirely possible that the Japanese could, if they wanted, strike the US Mainland.

It can be questioned why they would hit Los Angeles and not San Francisco, Seattle or San Diego, all of which had large navy bases, but the question is 'capability', not 'intent'.

However, this would not be not their only asset. The Japanese also developed a class of aircraft carrier specifically to attack the US mainland. This was the I-400 class, in Japanese, the Sen-Toku-gata sensuikan or special purpose submarine, each submarine capable of carrying three aircraft. However, although the vessels had been conceived prior to the Battle of Los Angeles, they did not enter service until late 1944. It wasn't until the end of the war that the Americans became aware of the existence of these vessels, the Japanese had been kicking around ideas varying from attacking the Panama Canal to make life difficult for US ships heading for the Pacific, to bombing Washington DC for the psychological value.

Of course, in the end, the only attacks on the US mainland came from the incendiary balloon bombs.