It’s really important to talk about how discussion of taxes in the US is so skewed.
Conservatives only like to talk about the federal income tax, but the US has a broad range of other taxes. Property taxes, sales taxes, state taxes, local taxes, workplace taxes, etc. And virtually all of those are disproportionate on the poor, not only in terms of burden, but in terms of rates.
For example, in most parts of the US, public schools are usually funded by local (by school district usually) taxes. Poor home owners and poor renters do not have relief from these taxes. People lose their homes because of taxes like this that they cannot pay because of poverty. And it also impacts the school their children attend. Because it’s a tightrope walk for poor districts to try to balance paying for education and not taxing their residence out. Which means poor kids get less school funds.
And that’s just school property taxes.
Federal income tax is the one Conservatives like to focus on precisely because it’s, while rather regressive, less blatantly regressive than most other taxes.
And even with federal tax return rates, the numbers are skewed by a policy that says that federal income taxes, if spent within so many days, are exempt from welfare income guidelines. So a lot of poor people overpay all year and use that as a type of savings and therefore it seems like their returns are inflated but really they were overpaying in their wages earlier.