But out of the top 10 richest in the US, only the Waltons are heirs. I would say it's a bit of a distortion, since the all of them combined I think is still larger than any other US individual.
Looking at Sweden, it looks like a lot of it is inherited, certainly most of the top 10. And like 1/4 are H&M, Tetra Pak, and Ikea alone. The new 'household names' are spotify and minecraft.
Norway is obviously smaller, but surprisingly, quite a lot of them got the three commas from their own businesses. The last-ditch cop out there is the typical Norway is in general an outlier due to being a highly developed nation with oil money. However, most of the billionaires are not there due to energy.
Also, it's a pretty unconvincing comparison to pick a small population country to benchmark the US against.
https://www.usnews.com/news/best-countries/open-for-business...
In goverment policy there is very rarely a closed form proof of any policy - we are almost always stuck with collecting large and small data points and needing to form a policy based on incomplete information and theory. But mostly it seems it’s matched up with motivations and biases - which are worth examining.