Switzerland has 8,570,146 population of in an area of 15,940 square miles, that calculates for a population density of 537 per square mile.
Virginia has 8,590,563 population in an area of 42,774 square miles, that calculates for a population density of 200 per square mile.
Naryland has 6,045,680 population in an area of 12,405 square miles, that calculates for a population density of 487 per square mile. Much of Maryland area is water, it's land area is just 9,776 square miles, that calculates for a population density "on land" of 618 per square mile.
FYI, The next state larger has 24,230 square miles is West Virginia, with little water area, so Maryland is closest in size to Switzerland as far as area is concerned.
Just checking a list of population density of the states at Wiki, the only states with a greater population density than Switzerland are:
New Jersey with 1,210 per square mile
Rhode Island with 1,017 per square mile
Massachusetts with 858 per square mile
Connecticut with 742 per square mile
Most of the USA's smallest states by area. None of them have as large a rail system as Switzerland, but most of them do not have a tall mountain range in them either.