We can be pretty comfortable saying that there was little actual threat of espionage from Japanese Americans during the Second World War. This is on account of the fact that the Japanese communities on the west coast were largly founded and populated by people who had arrived or were raised by people who had arrived around the turn of the century (~1880-1918). During that time Japan and the US had fairly cordial relations and the people arriving from Japan were very much pro-American.

I used 1918 as an end date up there because things started to sour after the end of the First World War.

• They attempted to have a clause included in the Covenant of the League of Nations that affirmed that nations must treat one another without prejudice toward race. This was important to them as,

• They were a highly developed industrial nation but still treated as primatives by the western powers.

• They had whipped Russia's ass in the Russo-Japanese War and kind of felt like they took the great power belt.

All that say to that Japanese emmigrating from Japan after around 1918 were much more patriotic and hostile toward the west. These emmigrants also tended to go more to Korea, China and Latin America than to the United States.

So to in summary: sure, we can never say there is 100% zero threat from anywhere we can be pretty comfortable saying that the Japanese community in America in the 1940s did not constitute any special threat of espionage.

Some further reading:
Washington State University