I’m teaching myself music theory while learning the guitar and I was hoping someone would be able to help me understand this issue.

The song is “Collide” by Kid Rock and the chords (according to a transcription I found online) are:

A-D-A-D

Bm-F#m-D-Bm

D-A-E-Bm

D-G-D-A

So I figure that this song is in the key of A major (right?) and I want to rewrite the chord pattern in number style to understand the structure and I get:

I-IV-I-IV

ii-vi-IV-ii

IV-I-V-ii

IV-??-IV-I

So the key of A major has a G# (dim), but not a G major. So what is G major in relation to the key? It’s some kind of seventh, right? Maybe a flat-7th-something?

Can anyone help?