The continental US is roughly 2/3 the size of Europe. Comparing Denmark to it is nonsensical given the differences in size.
IDK if size really matters here. Connecting Chicago to Milwaukee (100mi) with HSR probably makes sense
there are many others too:
Chicago-Indianapolis (200mi)
Chicago-St Louis (300mi)
Chicago-Pittsburgh (500mi)
so many good connections
We have freight rail connecting that already. Size should matter here because the population densities are not the same.
I think size should matter more.
In USA/Canada we end up with population pimples with little in between. This is perfect for HSR, since there are very few required stations between primary cities.
Ottawa-Montréal, for example, is ~200km apart with no major centers in between, so an HSR can cross that distance with no stops
Toronto-Montréal is ~550km apart, with one possible stop in Kingston if the train splits for Ottawa. Again an HSR could make great time here. With the TGV’s 270kph station-station time, it would be 2 hours, slightly faster than flying + security (2h10-2h30) and less than half the driving time.
I’m knot as knowledgable about US geography, but I’m positive there and many city pairs like this on the east and west coasts.