The US Census Bureau’s Bureau of Labor Statistics conducts a Time Use Survey to find out how much time Americans spend in certain tasks. Such as religious activity (prayer, Bible reading, church, etc).
For working Americans on an average weekday, the amount of time spent on religious activity is just 2.4 minutes per day.
The Wall Street Journal has compared this to other activities: (Yes, we spend 133x as much time watching television as on all spiritual activities).
The Washington Post has compared it across the states.
Unfortunately I believe the situation is worse, because this includes the 1% of Americans that are Catholics who attend daily mass (extrapolated from Georgetown Research).