[adrianmonk]

The US does make some adjustments based on income. The Affordable Care Act introduced the Premium Tax Credit which does this.

The way it works is the government subsidizes the cost of buying insurance. The money is given to you as a credit against income taxes you would otherwise have owed. (With most tax credits, you wouldn't receive the credit until after the tax year is over, but this credit has a special provision to receive monthly payments in advance.)

The amount of the credit is based on the cost of insurance (which varies by age and location) and it is also based on your income level and size of household.

The credit is for people just above poverty through the lower part of middle class. It phases out as income gets higher, and people with a comfortable middle class income receive little to no credit. At certain income levels, the credit is pretty substantial (as it has to be to cover the high cost of insurance).

More info: https://en.wikipedia.org/wiki/Premium_tax_credit