In the movie Rocketeers the gangsters who were working unknowingly for the Nazis switched immediately sides after the hero revealed the identify of their employers. I think there are also many other movies where gangsters are depicted as patriotic.
Given their influence in the underworld the Mafia and other criminal groups could have gathered important information and support which is not available to the legal or military system. Is there any indication that American gangsters in general were willing to help by e.g.
- giving tips to authorities if they observed suspicious activities (e.g. spying) in their district
- watched channels for smuggling
- accept disadvantages and losses by not working together with war-time enemies.
The important thing is that the gangsters did not have any advantage by working with the authorities (for e.g. money) so that the decision was triggered by patriotism.
Essentially, is the movie depiction of patriotic gangsters unadulterated kitsch or has it a real background?