None that ever came to life really. While one of the main events that seemed to prove the existence of insurgents, the attack on an oil facility by an I-Boat in February 1942, came into a much different light after the war.

During the war thanks to uneven blackout applications it was assumed 5th Columnists had guided the attack from shore. Turns out the subs skipper had previously been a merchant officer on a tanker that had visited LA and knew the area somewhat. While we must also consider just how much some decision makers were looking for facts.

Some were deeply troubled for instance by the Niihau incident in the aftermath of Pearl Harbor, but even now decades on with access to surviving Imperial records there has been no smoking gun as it were to point to any organized insurgency. While some decrypts of prewar chatter between Japanese embassies points to efforts to foment loyalty in target groups, both their own calls for redoubled efforts, and US investigations like the Munson and Ringle reports point to little success on that front. And statements by officers like General DeWitt that the absence of attacks a few months into the war MUST mean that they are simply waiting for the right time to strike, certainly helps imply that 60 years of racial tension were playing a greater than 0 role in the decisions made.

We can also look to the experience of the Hawaiian Islands. Over 1/3 of the prewar population were Nisei and Issei, and while a % of them were locked up as rable rousers or even shipped to mainland camps, it was never attempted wholesale, the population was simply too important in keeping the islands economy functioning. And despite the plethora of military targets, even accounting for martial law, no notable attempts at sabotage occurred.

The vast majority of govt, and academic analysis of the "Japanese Question" following the war has come to similar conclusions. That it was a heavy handed solution in search of a problem that fundamentally did not exist at any level that could endanger the war effort.