Compared to Uwe Boll's Rampage
*Some spoilers for both films*
So, I could compare this to Falling Down, but that just seems unfair.
Rampage explores many of the same themes: a society in decline, a disillusioned loner, condemnation of a complicit media. So let's compare and contrast. Key differences:
Bill Williamson in Rampage has a motivation. At the end of the film, it's revealed that the apparently suicidal rampage is actually planned to let Bill escape unidentified with a large sum of money. In contrast, Frank in God Bless America is simply acting out of bitterness. He is a misanthrope, but it's made clear throughout the movie that his actions are having the opposite affect that he intends. The Fox News reporter he kills correctly predicts he will be viewed as a martyr. Both protagonists are acting out of nihilistic rage, but Bill at least has a reason to do what he does, while Frank's supposed values are in contradiction with his actions.
The love interest. Frank apparently runs into the one other person he can respect in Roxy. The only problem is, she is an obnoxious, self-centered, intolerant person just like everyone Frank is killing. Again, it's hypocritical and undermines Frank's moral authority in the movie. Having a young girl throw herself at the protagonist, and for him to rebuff her advances is a very manipulative plot device that is suppose to make Frank appear to be a gallant chaste hero, while still providing a traditional manic pixie dream girl love story. Why does Frank scoff at the idea of sleeping with Roxy, but not hesitate to burn a girl of the same age alive in her car? Rampage's Bill simply kills indiscriminately. He frames his best friend out of pragmatism, as he knows his friends anti-establishment youtube rants will create a plausible motive for the killing spree. Bill understands the problem doesn't lie with individuals, but with society as a whole. Therefore no one is particularly to blame, or conversely, innocent.
The politics. Both films lampoon right-wing nutjobs pretty harshly. The difference is, Rampage also acknowledges the deficiencies in left wing politics through Bill's conspiracy theorist friend, while God Bless America panders for all it's worth toward liberals fed up with the Tea Party, Fox News, and the religious right. Godthwait throws feces from one side of the aisle, while Uwe Boll rejects the entire political system and cultural system that got us to this point in the first place. Boll's film embraces a purely nihilistic subversion of modern American capitalism, while Goldthwait cherry picks some symptoms and smugly reinforces one of the two pillars of this system.
Advantage: Rampage. Uwe Boll, the "Worst Director in The World", crafted a better movie than this in basically every way. I haven't seen Rampage recently enough to compare the technical savvy of both films, but I'd bet good money that Rampage's stylization would come out on top there as well. Rampage is like a brick through a window; a pointless, angry attack on modern society. God Bless America is a pandering, hypocritical, uninsightful jerk-fest at the expense of the easiest targets around.