According to data from the company comScore for the month of June 2017, Facebook is the most used native application on mobile by users in the United States. Specifically, 75.7% of users used it at some point during the month.
Second place was occupied by the YouTube video app (67.2%), while another Facebook app, Messenger, was the third most used (65.4% of users).
The following graph shows the 15 most used apps in the United States. The first 7 are owned by the two great internet giants: Facebook and Google.