What is this soft power and what can the US do with it?
Soft power is spending pennies to convince other countries to do your dirty work.
How much of that actually came from soft power rather than "hard power", like USA actions in WW2?
Some people mentioned the dollar as the global reserve currency, but there's also the use of English as the global lingua franca, the US being the largest global destination for talent and investment, and countries (previous) willingness to make sacrifices or deal with the US on less-than-perfect terms out of a sense of shared culture.
Basically a neoconservative-esque sentimental view of the USA as "the good guys" on "the global stage" (although many would rightly recoil at the comparison to neocons).