Mentioned it elsewhere in the thread, but I wonder if this isn't a different operating regime that's possible only under very high economic growth. A country starts projects that deliver quick and absurdly high returns, allowing them to start more, larger projects for more of absurd returns - all that over couple decades, allowing the expertise to develop and remain in house, always busy, enabling delivering even larger-scale projects quickly. Eventually, the returns start being smaller and smaller, until the government starts getting cautious about starting new projects, slowing things down, leading to evaporation of expertise, increased costs, etc.
Kind of like a scramjet engine, or a nuclear reactor, or I guess plenty of other advanced processes (including a technological civilization itself). You may need to boost yourself with a rocket to achieve a velocity at which a scramjet can start operating, but once you get there, you can start going much faster. But, if for some reason, you slow down below the threshold, the scramjet shuts down, and now you're going slow, and can no longer turn the scramjet back on, because you no longer have a rocket to boost you to its minimum operating point.
Under this view, USA's influence is attributable to a one-off leap. Seeing another country going through it now doesn't mean they'll overtake the US in the future - instead, they might run out of steam roughly at the same point the US did.
