Also even before the war started both ends of the Canal were heavily patrolled both by aircraft and ships. The US was well aware of the choke-point that the canal presented a potential adversary. There were several Destroyer squadrons and Patrol aircraft squadrons assigned to both ends of the canal. Any unidentified sub or ship would approaching would be investigated. It would be possible but difficult to get a sub close enough to actually mine the approaches even if you get Japan to break their doctrine to try it and break enough logistics loose from their already tight logistical schedule for what is basically a pointless exercise since the number of subs that they could send that distance would not make any difference at all in the Americans ability to use the canal. The US was already upgrading the defenses prior to the start of the war so attacking will not change the amount of force the US puts there. The US already had several patrol wings and fighter wings stationed there so it will not change the number of aircraft stationed there. The US already had a heavy naval presence, it might add to the number of destroyers assigned, or maybe not because the US was already scheduled to add two more squadrons of DD/DEs to each end of the Canal during the first part of the war anyway. So the Japanese spend fuel they can't afford, probably loose one or more subs they can't afford, maybe sink one or two ships if they get lucky and don't really impact what the US does at all.
Basically a pointless exercise for the Japanese - even more so than what they did iOTL.
Basically a pointless exercise for the Japanese - even more so than what they did iOTL.