Why is the default always to blame poorer countries?

The US is one of the largest contributors of CO2 in the world. The per capita argument is silly: They're a single, centralised source of pollution. Just regulate it already. The impact would be phenomenal.

As for the poorer countries: How about the wealthier nations that outright stole the mineral resources from us start paying that money back in the form of a solution rather than having their denizens pointing obese fingers at us?

I'm not saying give the money back (would be nice though), but how about spending that ill-gotten gain on progress for a change?