A common criticism of passenger rail investment in the United States is that, while passenger rail may work well enough in various countries of Europe and Asia, it will not in the United States due to the size of the United States and the lower population density as compared to those nations with successful passenger rail programs. This is, of course, a complete misrepresentation of the projection and rationale of the situation.
While the United States is indeed far larger than any of the countries which have built out a high speed rail network, the passenger rail investments proposed for it are not scaled up to the size of a continental empire like the United States, but rather are similar in size and scope to those already built. These are regional networks, existing either entirely within a state (such as is the case with California High Speed Rail) or across a small selection of states (such as the Northeast Corridor). The emptiness of Montana and Alaska is irrelevant to such considerations, therefore, as it is most appropriate to consider the size of the region in question to European or Asian analogues (as has often been done with California and Spain, which share a similar size, population, and density).
However, it is also useful to note that European Russia (that is, those portions of Russia located west of the Urals and containing the large majority of the Russian population) soundly defeats such an argument. While 78% of Russia’s population lives in this territory, itself about half the size of the continental United States, the population density is still extremely low. Whereas the average population density of the United States, even including Alaska, is 87.4 persons per square mile (rising to 103.5 once Hawaii and Alaska are removed), that of European Russia remains only 10.5 per square mile. Yet Russia maintains a high degree of passenger rail operations. Indeed, it recently placed an order for an additional eight Velaro high speed train sets for service between Moscow and Saint Petersburg. To suggest then that the United States, which possesses ten times the population density, is unsuitable for high speed rail, is quite fallacious.
Consider as well the Greater Los Angeles and San Diego areas. Combined, Los Angeles, Orange, and San Diego Counties have a land area of 9,050 square miles and a population just shy of 16 million. This makes for a land slightly smaller than the Kingdom of Belgium yet nearly 50% more populous. The Swiss Confederation, famous among transit proponents for its high degree of public transportation use, has a population of 7.8 million residing in a total land area 15,940 square miles. There is no rational reason why the United States cannot attain such high degrees of mass transit usage when, with the exception of certain areas in the midwest and Rocky Mountain areas, it has areas far denser than even highly notable European nations.