"he is the one who enables us to live in peace with each other". This emphasizes that Jesus alone is the reason that Jews and Gentiles can worship God as one peaceful community.
"he made it possible for Jews and Gentiles not to be hostile to each other anymore". Paul is speaking of Jews and Gentiles being hostile to each other and unable to worship God together as if they were on different sides of a wall. Because Jesus died, Gentiles as well as Jews can now worship God.