Residents of states also pay state taxes, and in high tax states those can exceed federal taxes so the "they also pay Puerto Rican taxes" line doesn't get them off the hook in any way.
I mean to say state on down, including property taxes, sales tax, gasoline taxes, local payroll taxes. Could be wrong but if you had a house that went up in value over the past few years I could see a situation where the federal income tax you pay is less than your property tax bill alone.
Edit: The more I think about it the very poor pay no federal income tax and the struggling pay very little, they could easily exceed it with cigarette or alcohol taxes for example.