This link is (on table 2) the PPP adjusted incomes for each decile of the OECD countries: http://www.oecd.org/site/piaac/Additional%20tables.xlsx
The US median 1st decile hourly earnings are $7.40. Austria, the Czech Republic, Estonia, Germany, Italy, Japan, Korea, the Netherlands, Poland, the Slovak republic, and Spain are all below there.
Australia, Canada, Denmark, Finland, France, Ireland, Norway, Sweden, and the UK are above there.
So I don't think that poverty is causing the US to underperform compared to the OECD mean or median.