Europeans do not have significant amounts of space to build housing supplies, that's why space/m^2 is much higher than here in the states, witness San Fancisco's trolley system that caused suburbanization (or at least enabled it).
Gas Taxes in Europe are double than here in the states[1], US gas is taxed at relatively low rates when compared to other nations. Used as a user tax here in the states, its predominant purpose is to fund roadway improvements and maintenance; however, it is used to fund transit and other items. In Europe, the higher gas tax is used to drive (good one Agustus) less travel and subsidize rail lines.
The trams / streetcars in Europe work because the suburbanization was stopped by high government taxes and forces the populous to pay more for a lower comparable standard of living.
[1] https://en.wikipedia.org/wiki/File:Fuel_tax_in_OECD_countrie...
*Edited for why, if you disagree, please provide an alternative opinion. I have taken the time to provide a discourse, if a downvote to it is necessary, then please provide a reason.