"
As we were, so perfect, so happy.
They'll remember, only our smiles 'cause that's all they've seen.
Long since dried, when we are found, are the tears in which we had drowned.
As we were, so perfect, so happy
The chorus talks about how a couple can seem really happy to those around them, even if that's not the case. It specifically says that even if their lives ended there, in that car, by the time someone found them, no one would be able to tell they were fighting, they'd still think that was a happy couple.