So the big car companies are forcing me to buy their product? It does not feel that way. Seems more like it is people in their capacity as voters and consumers which are driving things this way.
Not 'forced' like at the tip of a gun, but the big car companies (and others) pushed to redesign cities (probably before you were born) to service the automobile. Neighbourhoods we razed to build roads, roads were widened, sidewalks shrunk or removed, public transport systematically attacked, etc. The history is well documented if you want to read about it.
And the huge corporations lobbying to outlaw import of reasonable cars..
I'd argue it has less to do with the "capitalist systems" and more to do with how obnoxious "slugging" sounds. Commuting in your own car guarantees (a) you have a ride and (b) you have flexibility. You can change you plans, stop by the store, run errands, anything your heart desires (plus, not deal with strangers everyday. Ugh.)
This isn't a pro-car thing. I've haven't driven a car to work in 8 years (I pay out the ass to live downtown so that I'm close enough to walk / bike). It just seems like "Well, that sounds like a pain in the ass" is a simpler possible explanation to why slugging isn't popular in the US compared to Big Business not wanting it to be.
Slugging isn't common because the capitalist system would rather everyone buy a car. Selling cars is big business.