How far Christianity has strayed from its Jewish Jesus is one of the ironies of history. A Jewish messianic movement highjacked by the Roman Empire to the point it became anti the real Jesus and only liked the platonic romanized version of a Jesus detached from
History and Judaism.

Americans thought they were special and their institutions would hold. But Americans are humans that too that can have all the ugly qualities of human history with the wrong leadership and incentives.
The institutions are only as good as the people that hold them and depend on the bravery of a few

When they could no longer persuade the people they had to resort to power over the people.

Also consider the theology of the apostle Paul in book of Romans New Testament. The whole gentile salvation is based on adoption into the story of salvation.