A great bit of activity San Francisco saw recently was someone renting out parking spaces as "office spaces" for like 2.50$ an hour. It pointed out that a similar space in a building would probably go for more like 10$/hour or more, highlighting how little we're valuing our street-side real estate.
"Denmark is approximately 43,094 sq km, while United States is approximately 9,833,517 sq km. Meanwhile, the population of Denmark is ~5.6 million people (321.0 million more people live in United States)" From a quick search.
Also, given the numbers I just posted, even if your 80 percent number is right, that's still a portion of the population doing long commutes, and that number of people is more than the entire population of Denmark!
Look, I've traveled in places with great public infrastructure and I really want the US to work very hard towards it, but I get tired of all the Europeans who always in any thread of this subject start ridiculing us without even fully comprehending how large the US is. Do we need to put major money and work into it? Yes. Does that mean it's actually feasible for people to get rid of their vehicles? Not yet for anyone except those in the best public transpo cities.
"Your argument is stupid" ... great one...
There are people with very long commutes in Europe too. I personally know people who commute 100km+ one way.
If you had to drive 75 miles to get to the next Walmart you probably didn't live in an urban area so any arguments against cars in urban areas don't apply to your lifestyle. You won't find public transport in the countryside in Europe either.