For the last year or perhaps three, travel within the USA has required middle names (not just an initial) within the booking.
Last year at LAX I had to change my OLCI QF BP showing my middle initial for a standard one showing my full name before I could go through security at TBIT.
From my recent experience (in May), I have used my first name and last name with no middle initials in all my US domestic bookings and there were no issues whatsoever whether it be ORD, LAS, SEA or JFK.