Exactly. The US isn’t being left behind. Trump is choosing to abandon a leadership position and others (China in particular) will step in. Will they be altruistic and benevolent or will they, first and foremost, look out for their own interests? (Not that the US didn’t do that.)
Leadership isn’t easily granted.
If that position is squandered during the next four years, Can it be reclaimed?
It would require a reasonable and charismatic President. No need to speculate who that could be now. Four years is a long time for Geopolitics. The world stage can change a lot.
It would also require an attractive, consistent and relevant domestic policy offer: building that and demonstrating its electoral success takes plenty of time. But that’s a separate debate, perhaps
I doubt it; America’s leadership position such as it was largely was a legacy of it being the only really intact major power after WWII. We won’t have that advantage in the future.