The major issue is safety. Bikers are much more (3.4x to 11.5x) likely to be fatally injured per mile travelled compared to people driving cars [1]. Better bike infrastructure is needed.
Yet despite that, the improvement in fitness from commuting by bike rather than car, is so great that switching to bike will statistically increase your lifespan in just about every city in the world. That’s after including the negative impacts of increased exposure to air pollution, and higher likelihood of being fatally injured while commuting.
Well sure, if keeping your car is important to you, then do what makes you happy.
For me switching to a bike meant more exercise without having to commit any extra time. Just swap on type of commute for another, duration didn’t even change due to congestion which is easy to cycle past.
Given the US rather extreme obesity problem, I would suggest that it needs all the help it can get when it comes to improving fitness.
[1] https://bicycleuniverse.com/bicycle-safety-almanac/