This new form of perpetual slavery was ushered into existance by a Papal Bull issused by Pope Nicholas V. See the TransAtlantic Slave Holocaust for more details.
Yisrael was expelled from the Land for being disobedient to Torah (the Law) and for serving and worshipping other Gods. From the time of the fall of the Temple in 70 AD until the present day we have endured various levels of slavery and captivity. Once we where disconnected from our land and our culture, the decline of your people has been well documented throughout history.