I agree with this take - Green Day does tend to mine the nihilist aspect of punk in general, but American Idiot is bigger than that.
As for what punk is…meh. There is a “punkist” mindset about what is and is not punk that is pretty amazing and ironic in its desire to establish rules for something that was about trying to break rules. I look back to this threadfor where that thinking can lead…(thread where posters are stating that original punk bands aren’t punk because, well, they aren’t *their definition *of punk…oy.)