When we focus on the federal income tax, we miss all the taxes that low-income Americans do pay. The payroll tax, for instance. And state sales taxes. And lots of local taxes. Indeed, 

Citizens for Tax Justice, a left-leaning tax policy group, produces a study every year showing the total tax burden for different groups once federal, state and local taxes are taken into account. And when you include all the taxes people pay, then, as you can see in the graph atop this post, it turns out that most Americans do pay taxes, and they in fact pay about as much as the rich.