Why were African-Americans, and "not" Europeans or American Indians forced into slavery?I am looking for a list of facts and/or educated assumptions.

Both good answers.  There were, however, European slaves in North America, although a small number.  Many were persons kidnapped in the British Isles in the aftermath of the Jacobite rebellions, and sold in the New World both in the Caribbean and the mainland British colonies.  Some were sold and then treated as indentured servants, but some were kept in slavery.  The earliest African slaves brought to the British colonies were treated as indentured servants and set free after seven years with pay and land, until 1644 when the Massachusetts legislature passed the "Body of Liberties" bill legalising chattel slavery in British possessions on the mainland.  The Spanish of course enslaved Indians, Africans and a great many captured British, Dutch and French sailors indiscriminately.

So while we tend today to concentrate on slavery in the New World as the enslavement of Africans, in reality blacks, whites and Native Americans were all enslaved at times.  Entire populations, such as the native Jamaicans, were exterminated by the Spanish.  And while Central Africa was nearly denuded of population by the slave trade almost all of those slaves were sold to Arabic countries or India, and the vast majority in the 1870s and '80s, after the American "Civil War" was over.