ANY sort of inherent human greed capitalizes on suffering. It doesn't magically disappear with another system. There is always a pareto distribution of wealth. The differences are in which metrics are the primary leverage for accumulation and the scale of the differentials (wealth disparity) along the curve.
Capitalism didn't originate the concept of resources, or politics, or even money. How can you justify blaming Capitalism for things that happen just as much, if not many, many orders of magnitude more in non-capitalist societies?
Conversely I think it is justifiable to attribute the enormous economic gains of that billion people to capitalism directly. It's an economic system and we're measuring economic gains directly attributable to investment, often replacing decidedly un-capitalist systems.
Consider your favourite successful startup and move it to Central America. Now consider what additional factors it needs to take in to simply operate. Take security as an example: Private guards acting with high aggression (machine guns) are a basic requirement in some areas. Compare that to New York (Hand gun).
It's not a reasonable comparison.
You're missing the point. The United State's functioning capitalism is a major cause of your hesitancy to call Central America's countries functioning capitalistic societies.