Why, it's accurate, according to this

The United States has emitted more CO2 than any other country to date: at around 400 billion tonnes since 1751, it is responsible for almost one-quarter of historical emissions; This exceeds the contribution of China, the world's second-largest national contributor, by more than 1.5 times;

Cumulatively the US has contributed far more to climate change then any other country, and since there's no major net carbon sink to offset historic emissions, cumulative emissions are what matters.

Most of that tonne of CO2 that was released from a factory in 1870 is still in the air today, warming the planet.