God chose Abram. God created a perfect relationship with the man, Adam, that was shattered with disobedience and resulting separation. God pursues returning creation to its reconciled state, through the offspring of the original being He created, Adam. We see then, God reaching to all humanity by establishing a covenant relationship back to the lineage of originality.
God chose Abram because Abram was a generation of Adam. God sought to reconcile creation back through the lineage of the man who committed the original sin. Reconciliation extended to a man through his offspring.
God's offer to humanity doesn't change, He extends it through the generations, He wants us to be reconciled to walk with Him face to face. He wants us to accept His love and knowledge of us, and then to reciprocate that love freely, and to seek knowledge of Him.
It is a beautiful revelation of the nature of God. Our original covenant in the garden was broken... and along with it came the curses of the ground, and of death... but God didn't leave it there. He also seeks to bring us back to that created state by again making covenants with the generations sprung up from the offspring of His original created being, Adam.
We are all Adam. We are all Abraham. We are all Noah.