And who wants to chime in their two cents about what the USA's "trick" is in maintaining its global pre-eminence?
On the question of whether there's a singular trick that's exploited, I'm not aware of anything in Tainter's writing that suggests this at all. There is the concept of Leibig's Law of the Minimum -- the idea that for any system (Leibig is speaking of ecosystems or populations) there's some one factor which imposes a constraint on the system. In that regard, you could could likely look at a single technology which is the operative constraint. But if you're looking at a complex system with multiple modes of failure, you'd be arguing precisely the opposite: that there are multiple technological tricks which aren't presently binding constraints but which, if any one of them failed, would rapidly become one.
There's no basis that the trick need be unique. I'd argue that they're anything but. Basic modalities include agriculture, construction, fire, transport, arms or weapons, and control over hygiene factors.
The United States' trick was in large part massive overwhelming self-sufficiency in resources, most especially energy.
See Vaclav Smil, Energy in World History, Manfred Weissenbacher, Sources of Power: How energy forges human history, or Robert Ayres, The Economic Growth Engine: How energy and work drive material prosperity.
http://www.worldcat.org/title/energy-in-world-history/oclc/3...
http://www.worldcat.org/title/sources-of-power-how-energy-fo...
http://www.worldcat.org/title/economic-growth-engine-how-ene...