Flew DUB-LAX in 2003 with AL, we flew direct to McCarren with America West, had to change terminal in LAX - about a 5 minute walk or there is a shuttle bus.
I have heard that one cannot book internal US flights by CC with a non US address anymore.
If you go to Opodo.com they will be able to book you right through (if you don't wanna drive), though when we checked this Opodo were more expensive by about 150 dollars for the EXACT same flights ! Suppose though at the time we could book flights individually.
The AL aircraft that we were on to LAX have individual TV's on the head rests. Not sure if thats changed.
Enjoy ! Eitherway Vegas is great for a few days !