This is a great song and band. I don't know what the second guitar is playing,
but this is the main riff.
Standard Tuning: EBGDAE
E|--------------------------0--1/3---------0-------------------------------|
B|-5p3p0-----------0--1/3------------0--1-----1----------------------------|
G|--------3--0h2-----------------------------------------------------------|
D|-------------------------------------------------------------------------|
A|-------------------------------------------------------------------------|
E|-------------------------------------------------------------------------|
[ Tab from: http://www.guitaretab.com/a/american-football/183501.html ]
E|--3p0---3p0----0h1p0-------0----3p0--------------------------------------|
B|------1-----1--------1---1---1-------1h3---------------------------------|
G|-------------------------------------------------------------------------|
D|-------------------------------------------------------------------------|
A|-------------------------------------------------------------------------|
E|-------------------------------------------------------------------------|
/ = slide up
\ = slide down
h = hammer on
p = pull off
b = bend
r = release
x = muted string
t = tap (with finger or pick)
~ = vibrato