Found this on Pol.SE:
The US relies on its higher income residents for an exceptionally large amount of its revenue. Almost half of the population pays no federal income taxes at all. The top % pay about a fifth of the overall taxes. ... The US is heavily reliant on its richest citizens to support the tax burden. If it reduced that, then it would have to do one or more of increase middle class taxes, reduce spending, or increase borrowing.
The answer links to https://taxfoundation.org/summary-latest-federal-income-tax-data-2016-update/ which provides some confirming(?) data points.
I would like to specifically ask whether it can be legitimately said that the US is heavily reliant on its richest citizens to support the tax burden?