However there's substantially more income inequality in the U.S., so GDP per capita won't capture the distribution of that wealth particularly well.

GDP per capita is pretty much useless nowadays.

It's useful in as much as it provides a basis for comparison between differences in the base standard of living between equivalent gdp/capita societies, like Finland and the US, which is what the parent was doing.

It's not, however, useful as the sole metric for evaluating the economic condition of a society.