> The US tax code has gotten more progressive over time, not less. The very high tax rates from the past were quite narrow in scope, they covered few taxpayers.

That's not how that works. The U.S. has become massively more disparate in income and wealth, which alone would explain why more taxpayers fall into high tax brackets: the middle class is evaporating, leaving a somewhat larger upper class (more high-income taxpayers paying a lot!) and a massively larger lower class (also more low-income taxpayers paying very little), thus shifting the balance of how much the wealthy pay for the poor: with less of a middle class, the wealthier are the originators of a higher percentage of the tax revenue just by mathematics. That's not the tax code becoming "more progressive over time," that's the US having more inequality over time.

But it didn't happen alone. It also happened under repeated tax cuts for the wealthy. The U.S. tax code has become demonstrably less progressive over time, just as the U.S. has become demonstrably less economically equal.

> The US spends the equivalent of 20% of its GDP on social welfare programs. That's higher than Canada and Australia, just slightly behind the UK at 22%.

Right, but that's because the health care system of "no preventative care for the poor, but massive spending on medical procedures once you're already dying" is incredibly inefficient. Single-payer healthcare is cheaper than what we have, demonstrated by almost every large country with it spending less (while often getting better results). It's not because the tax system is progressive, or because the social safety net is somehow better or larger than countries with free healthcare and cheap higher education.