Having watched the film, here is what I know about the plot of G20.
President Viola Davis is trying to solve world hunger and feed farmers in Africa, or something like that, at the expense of American voters (her opponents say) or to keep the dollar from collapsing (her other opponents say). It was never clear to me how these facts interact, nor how switching to a new worldwide currency[1] would fix hunger. Or necessarily how it would destroy America, for that matter.
Anyway, what’s important is her plan is somewhat unpopular, her teenage daughter is extremely rebellious and tech savvy, and the whole family is headed off to South Africa for a G20 summit where she will try to convince the other major nations of the world to sign off on her plan, whatever it actually is. Unfortunately for her and other world leaders[2], Homelander (but without his powers and with a non-specific accent that is later claimed to be Australian, but I dunno about that) has a plan to kidnap all of them and destroy the world economy so he can make some money off crypto.
Premise established, now it’s time for the explosions and gunfire. The only thing that separates this from any other political action movie is that Viola Davis is the action star. Gonna be honest, that’s what won me over here, and now that I’m out the other side? No regrets. (But I doubt I would have gone to a theater for it, so nicely done, Amazon, for going straight to streaming.)
[1] If that’s even what was being proposed? I am forced to admit that I must have missed some of the early film exposition, or else this never even tried to make sense. One of the two.
[2] Including Russia, China, Turkey, Britain, South Korea, implied Saudi Arabia, and 13 unspecified others, though one supposes the actual Group of 20 is fairly static and it would be easy to learn who would be expected present.
[3] Depending on how you count, there were either a lot more than 19 captives, or there were 18. But that doesn’t flow as well I suppose.