At no point in the war or before did either Germany or Japan in anything approaching a serious manner consider attempting a landing on the US mainland.

The Kriegsmarine was simply a broken force in so many ways, from design, to organization, to political leadership. It bounced between multiple concepts of operations and never got good at any of them enough to maximize resources expended. And throughout the war its first and in many ways only concern was how to beat the Royal Navy.

But enough about that small unfortunate force the Japanese at least better understood the requirements of fighting a hemispheric naval war. Fueling, transit time, safe harbor, and ship endurance did more than anything to determine what was within a force's ability to strike at and what was not.

And that put the West Coast WELL outside the ability of the IJN to sustain operations there. Submarines are one thing and can be designed for long range raiding cruises and easier to clandestinely refuel and provision. A large task force with fuel guzzling battleships and carriers, short ranged destroyers, and dozens of transport craft would simply not have been able to be sustained. The IJN additionally was relatively inexperienced and underway refueling, having only gotten serious about the practice just before the war, and the need to do so on the way to Pearl Harbor became a motivating factor to learn, and the small number of fleet oilers additionally limited the size of task forces operating far from bases at length.

And that makes sense, the Japanese strategy against the US was fundamentally defensive in nature. It was to use the Kido Butai as a perfected raiding force(which also limits its utility in supporting sustained landings and land battles in contrast to late war USN carrier forces) to punch the US in the mouth. If this did not result in peace then the operational freedom bought would allow the IJN and IJA to seize the Southern Resource Area and then fortify a string of island bases. These islands running from the South Pacific up through the Mandate Islands of the GIlberts and Marshalls would provide a series of mutually supporting bases and airfields to bloody US counterattacks. This then would be backed by a second line of bases in the Marianas as their anchor. Once the bloodied US forces would have reached this inner line then the final battle of decision would be sought. The well rested and supported Combined Fleet would seek out and destroy the US fleet as they could. This was at least the mainline thinking inside the IJN.

For some additional reference on the limited nature of IJN amphibious capabilities and ability to power project ashore we can also turn to COmbinedfleet.com. Written by Parshall and Tully two of the leading historians of the Pacific War we have this very topical article. It examines the issues related to just invading Hawaii, both in December 1941, and as a follow up to a reversed battle of Midway. And why it just wasn't in the cards. http://www.combinedfleet.com/pearlops.htm