It's only decline if the US is doing worse than it did in the past. But this data seems to be a single snapshot. It would be good if someone could find past results and see if there has actually been a decline.
If you interpret the title as referencing a general decline (as opposed to a specific decline in these metrics) and attempting to explain that decline with the charts presented, then perhaps you'd accept this as evidence of a decline: http://www.wolframalpha.com/input/?i=US+minus+China%2C+US+mi... ?
Edit: I realize this is a rather liberal reading of the title. I'd argue the title has been, not unexpectedly, sensationalized.
The "decline" is based on that in the US younger people do worse than older people when compared to other countries. Think of the study as a core sample.
"Some countries are making progress from generation to generation. But in the United States, as in Britain, the literacy and numeracy skills of young people coming into the labor market are no better than those who are about to retire. Americans who are 55 to 65 perform about average in literacy skills, but young Americans rank the lowest among their peers in the countries surveyed. The problem is not so much that the United States has gotten worse, but that it stood still on indicators like high school graduation rates while its foreign competitors rushed forward. Beginning in the 1970s, other developed nations recognized that the new economy would produce few jobs for workers with mediocre skills."
Yes, it shows that other countries are catching up, but every country in the world affects every other country through import/export. If every country in the world were at the economic level of the US, our products would cost much more and every American's purchasing power would go down.
If we put money aside and look at social aspects like education or corruption, I don't think the US has ever topped those charts recently. The Scandinavian countries seem to dominate those types of charts year after year.
