Japan eh?
The idea definitely germinated in the Autobahn. The proof is in the pudding. (I just love that expression.) The US used its scaled interstate system to achieve a range of product and population distribution that was unprecedented. It also clobbered passenger rail in the process. Conversely, Europe, not having a well developed interstate (would need to be inter-country to even scale to a few US states), did not develop or extend its road system in the way the US has. Instead, it built trains.
It's not a matter of one is better than the other. Each one is better for the countries involved because of their size and geography.
[0]: https://www.statista.com/statistics/449781/europe-eu-28-time...
[1]: https://en.wikipedia.org/wiki/International_E-road_network#/...
If we're talking about all motorway style roads, there's some additional roads in the US that qualify: 67,353 miles or 108,394km[2].
[0]: https://en.wikipedia.org/wiki/Numbered_highways_in_the_Unite...
[1]: https://en.wikipedia.org/wiki/United_States_Numbered_Highway...
[2]: https://www.fhwa.dot.gov/policyinformation/statistics/2017/h...
It’s even standardized: https://en.wikipedia.org/wiki/International_E-road_network
That sounds more similar to the US Numbered Highway system than it is to the Interstate Highway System: https://en.wikipedia.org/wiki/United_States_Numbered_Highway...
The Interstate Highway System is a different system - entirely controlled-access motorways, with a minimum of 4 lanes, divided, and no at-grade crossings.
Tldr the americans interstate system is nothing more than a copy of the german autobahn... And was never something unique.