What makes you think that European highways don’t connect between countries? You can cross the continent without leaving a motorway.
It’s even standardized: https://en.wikipedia.org/wiki/International_E-road_network
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.