“Until, by the 1600s or so, the people who would be Americans in the “new world” did something truly repugnant and horrific — they began an international slave trade.”
While I dispute nothing else in your post and wonder over the same thing, I have to tell you that ‘the people who were to become Americans’ did not start an international slave trade but merely expanded it over an ocean. For about a thousand years before then, the Arabs had been running an international slave trade out of Africa with unbelievable numbers of casualties! You can find this and more in John Adembillah Azumah’s The Legacy of Arab Islam in Africa. There are also some videos on Youtube which can tell you more.