The US has an insanely outsize prison population. It didn't get that way without people being arrested by a growing army of militarized police, and, in most cases, plea bargaining with an aggressive prosecutor.
That doesn't really have anything to do with the proliferation of laws. Almost all prisoners are in prison for a narrow range of offense classes: violence, theft, and drugs. At the federal level there's also a lot of immigration violators.
The explosion in prison population is not related to an increase in the rate of arrest and conviction. It's related to a huge increase in the number of years of incarceration per offense.
