Basically, it reduces transaction flows, which reduces wealth. Innovation.
Currently distribution of wealth is off, and innovation isnt looked for structurally in highly developed countries, where the population will shrink (roughly).
(Thinking behind it goes as follows. You can develop other countries with current tech - and make money. And when they reach roughly your 'developmental stage' (work expertise), you'd want to push innovation spending on countries, where the middle class is growing (more 'first adopters'/customers) - in absolute numbers. (More profit per investment spending.) Part of that growth you are looking for is natural growth (population growth).
(Distribution of wealth is off, because everyone can produce in mexico basically 'overnight' at least most goods that are still produced in the US - which means, no union power possible. Internationally the issue (for developed countries) is globalization (Think mexico example, extrapolate to the world.). Both mean - increased production (because more markets), but lower wages in developed countries.)
Also - many large problems can only be addressed by 'internationalism'.
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Also outlook of nationalism is problematic. In the US maybe less so than elsewhere. Because it leads to less trade contact, more cultural myth building, more animosity - and in the end more wars. (Just because of economic imbalances.).
No its not. (At least not alone. And at least not 'to a large extent' 'in every country'.) Too many problems arise out of the use of nuclear energy. Mostly waste and 'end of life safety' related. And upfront cost (its not that cheap to build nuclear reactors at scale).
Nuclear reactors are touted as a fallback for renewables at scale. (So when night, and no wind blows, add nuclear capacity). Because energy storage is such an issue (with anything not oil, or coal, ..

) (you loose so much through storage). But even there, people would rather not rely on them in many countries, and find alternatives... Which actually, is partly cost driven, even at this point.
Renewables will come. The question rather is when. And 'how much of their innovation is produced in my country' (not for innovations sake, but for 'value add' (value that is generated in country, through labor)). And if the answer is 'factories are fully automated by then, and china controls the ressource market' - well... Not much money that stays in the 'producing country' (even if nationalistic

) I'm afraid...