You have hit the target on this. America’s success points up the lack of success in other countries. This absolutely galls them, so they must come up with some excuse as to why they are not doing better. The easiest excuse, and lie, is that they are not doing better because America is keeping them down.
The Left somehow thinks the poor are incapable of improving their lot and need to be treated like farm animals.
On the other hand, a Meritocracy says to the Poor, "take a training course at the local technical school, learn a trade, make a living...RISE UP OUT OF POVERTY!"