DC has the highest spending per pupil and the worst results. Why do we spend the most per pupil in the West and have such horrible schools? Money, is not the problem. It's the schools themselves and the lack of accountability. No one harms schools more than the Union of Failed Teachers
First off, what you have posted isn't entirely accurate. While the US does have the highest spending per capita in the West, it also has the highest cost of living of any country in the First World. You're 7th overall in spending as a percentage of GDP, out of 32 countries. It has the highest spending on post-secondary education in the world, by far, which pushes your overall average up, and give the US the most expensive post-secondary schools in the world. It also has the highest dollar contribution by parents in the First World, meaning private school tuition.
The US government spends a "below average", meaning a below average percentage of its GDP on primary and secondary school educations to other western nations, and spending in poor neighbourhoods is well below the national average. As well, US schools have expenditures for security, which other countries don't have. It's a different environment.
The raw $$ are pretty meaningless because the cost of living varies enormously from one country to another.