You're comparing the number of people who cycle to work with the number of cars in the US. That's an odd comparison.
In spring 2017, the number of people who have been cycling within the last 12 months amounted to 66.21 million. [Source](https://www.statista.com/statistics/227415/number-of-cyclist...). Given that some people own two vehicles, I think you'll find similar numbers for people who own cars and bicycles.
And part of the reason people don't cycle to work is that there aren't safe cycle routes to their work. If you build your infrastructure for cars it forces peoples hand. The Netherlands has extensive cycle friendly roads and adoption is much higher.
In spring 2017, the number of people who have been cycling within the last 12 months amounted to 66.21 million. [Source](https://www.statista.com/statistics/227415/number-of-cyclist...). Given that some people own two vehicles, I think you'll find similar numbers for people who own cars and bicycles.
And part of the reason people don't cycle to work is that there aren't safe cycle routes to their work. If you build your infrastructure for cars it forces peoples hand. The Netherlands has extensive cycle friendly roads and adoption is much higher.