Most of the US is nowhere close to as densely populated as Western Europe, even excluding Alaska and the mountain states. You can't just look at the land area a

Most of the US is nowhere close to as densely populated as Western Europe, even excluding Alaska and the mountain states. You can't just look at the land area and population and make a naive calculation of density. Western Europe's population density gradient is much sharper than most of the US. Only the coastal corridor of the Northeast US really comes close. The gradient of the populations is important because it tells you how many people are within a usable range of the train stations. Even if you've got a high speed line between Madison and Milwaukee what in the hell are you going to do once you step off the train? Neither city has impressive public transit and both are very spread out. A high speed link might save a boring drive between those cities but that savings would get eaten up by the intra-city travel.