What feature of life in the U.S. might be used in an argument against the author

Not all states in the US require ANY minimum amount of recess for elementary schools. The states that DO have minimum recess time laws are only 20 minutes.
School playgrounds are not funded by states.  If a school wants a playground, the parents have to donate money and fundraise for such things.

Most cities do not provide designated lanes for bikes.

It is rare to find bike trails of anykind leading to schools so students living just blocks from the school have to be driven because of unsafe crossing and no bike lanes or sidewalks.

Children under the age of 10 are looked down on if a parent is not with them at all times so free bike riding is rarely observed among groups of kids.

Most parents work outside the home in the US and cannot supervise kids all day outside when they are playing.  Free park play is not an option for elementary school aged children without direct parent supervision in the US.