Cool People who did Cool Stuff can remind you. One small example, teenage girls were going around murking nazis on the regular. They found others to help. Unrelated to the US, but a cool story of community resistance.

where do you think the Partisans came from?

Literally everything that is spy work, subterfuge, being an opposing army, etc is community organizing of some kind. You have to find the community within that wants to take the risks to do these things.

So, to answer your question, 100% community organizing stopped the Nazis.

Are we counting the initial formation of the Soviet Union as community organizing?

Considering the USSR by and large killed more Nazis than anybody, I'd say a shitload of community organizing stopped them.

Show up alone, you get arrested. Show up with 100 people, you get shot. Show up with 100,000 people, now we have a movement. Will your neighbors show up with you? Or will you face the Nazis alone?