Yes, SpaceX could only happen in the United States. But let't not pretend that the whole American package warrants the 'favored and exceptional nation' badge that so many seem to want to bestow on it, which is what this American exceptionalism is all about. Shining city on the hill and more of that kind of crap.
One cannot ignore that they did their later work here. Not there. As did many others whose own societies collapsed or otherwise failed them.
In any case, I’m arguing a narrow argument: that a company like SpaceX could only have been founded, when it was founded, in America. Because of its certain characteristics that are an exception in the set of the world’s cultures. (One among many: its unique ability to assimilate and positively appropriate from immigrants.) That doesn’t mean it’s faultless; that’s a straw man.
The US is not unique in that regard. Australia and New Zealand are very comparable in that way. Canada probably belongs in that list too.
I agree that, in the contemporary world, SpaceX could only have happened in the US. But that's because of economic factors (government funding for the space industry, easy and plentiful access to venture capital, a low regulation business environment.) That particular combination of economic factors is unique to the US. Being exceptionally welcoming to immigrants is rare but not unique.
https://en.wikipedia.org/wiki/Operation_Paperclip
In a more just world they would have stood trial in Nuremberg.
Having had a bit of a ground-level view of this going back over a decade, yes, America is exceptional in this respect. Lots of people tried to do private launch overseas. Trivial barriers like explosives licenses stopped most at the gate. The sole success stories are in the U.K. (Skyline) and New Zealand (Rocket Lab), with the former stretching the definition of "success." Meanwhile, America has SpaceX, Blue Origin, Virgin Galactic and a trove of others.
The permissiveness and commercial latitude the U.S. government affords Americans is unique. The protections American law and culture afford private property is similarly quite extreme. These facets come with downsides. But in 2001, I can confidently say that had Elon started SpaceX anywhere but in America, it would have dismally failed.