It's not the travel or jet lag from travel. In football home-field advantage is created by conscious and unconscious referee bias, body-clock issues, and for the unprepared, crowd noise. We "struggle" on the road because every team "struggles" on the road and no matter how well we can feasibly play on the road, it will always pale in comparison to how well we play at home. This is a non-issue!
While it's true that, over time, home-field advantage has remained constant across the league, statistics also back up the fact that west coast teams playing in the east have a significantly worse winning percentage than east coast teams playing in the west.