[digital-cygnet]

The comparison of real household income to vehicle CPI doesn't really make sense. The "Real" in the first stat refers to the fact that it's CPI-adjusted, while the latter can be thought of as being in nominal (unadjusted) terms, as it is itself the adjustment factor. This means the first number is already lowered to account for the second.

Put another way, if "CPI - New Vehicles" accounted for all of CPI, the comparison you give would mean that people get 9% more car for their income than they did in 2001.

To do this right you'd need to compare nominal median household income, which has gone from ~42k to ~67k over the period in question, an increase of ~60%. This leads me to believe that the ability of the typical household to afford a car increased 2001-2020

Nominal median household income: https://fred.stlouisfed.org/series/MEHOINUSA646N