How would you musically identify blues and/or country music?

I asked a musician friend recently what defines the blues – other than lyrics – and he said it’s the chords. I’m not quite getting that. To me it’s more the rhythm but maybe also if it’s in a minor key. I’m also listening to country some and wondering how almost immediately – again discounting lyrics – you can define a singer as country or a song as country music.

What would you say are the musical characteristics of either or each?