The author's literacy, numeracy and problem-solving ability seem questionable. Decline means descent: going from a higher level to a lower level, of which the article demonstrates exactly none.
There's an implicit assumption that we used to be on top, although it's not supported by data (and I'd hazard that the data would not support it).
It's another form of nostalgia, really. People think the US was so great and wonderful in the past and now it's crap. It was crap all along, really. Happened to be some good crap, and still is in many ways, but crap just the same.
If the USA wants to return to the global domination it had in the 1950s, the answer is clearly another devastating world war that leaves the USA is the sole advanced nation untouched, since that's how we got to that position previously. Not by education or technology or resources or innovation (although there was plenty of that too), but by having all the competitors tear each other to pieces for years. Now the world is enjoying relative peace, and that means we're not so special anymore!
I think you're right, but only partially. In addition to being the only industrialized nation in the world left mostly untouched by the war, it was also the prime destination for the world's best and brightest looking for someplace to escape to. Add to that the fact that the US was already in the mindset of trying to prove itself equal to the "traditional" superpowers (England, Germany) and that it found itself immediately after the war in competition with a genuinely scary foe, and the US really had nothing to loose by going all out.
Peace is not the US's only enemy. The US also suffers from that most damnable of afflictions: success. Physical isolation means that the US doesn't have to worry about aggressors on its borders, but it also means that the US feels less of a push from its friendly competitors. Why invest in science or education? Why not just enjoy having the world's largest military by a long-shot? Why not enjoy the land? the natural resources?
That the US will eventually loose its top spot is certain. The problem is, when the US finds itself no long top dog, will it have the means to kick itself back into gear. That, I think, is the real damning implication of these graphs.
Being better educated won't prevent the eventual decline of the US, but it will determine just how far down that decline goes...
