How was the impact of computers in the 1990s similar to that of the car in 1920s? 

There are many ways in which this was true.  Let us look at a few.

• Both allowed people to be exposed to new things and new ideas.  Cars allowed people to physically move around and see new things.  Computers gave more access to information about ideas and places.
• Both provided for new forms of entertainment.
• Both could be seen as endangering morality.  Cars gave young couples ways to have privacy.  Computers could be used to access pornography.

In both cases, the new technology completely changed the ways in which people lived their daily lives.