Matin
Doesn't your "parting shot" put a big hole in your argument that we must show the rest of the world what they can become?
Besides, few nations have the advantages the US has always had since the first colonies were established: wealth and massive natural resources. It is doubtful that they can all aspire to America's greatness.
As for your "Darwinist" approach to the problem, I would point out that natural selection is wasteful and random. It is only after countless evolutionary dead-ends have been encountered that a step forward might occur. "Responsibility" and "consequences" are not linked ideas - in fact "responsibility" does not feature at all.
But I'm prepared to adopt your attitude: let's lead by example. Let's show the world what we have the capacity for. Let's double international aid and think about increasing it more. Let's treat the poor as if they are worthwhile people, not stupid fools who deserve their fate because they were born that way!