In my previous comment I mentioned that the colonizers first destroyed the existing structures, so if the Europeans first hadn't colonized the continent, then there couldn't have existed any bad transition _from_ colonialism either.
In other words, the first sin was to colonize the continent in the first place, destroy existing civil structures, and exploit the land and the population as they did. The second sin was to very abruptly abandon them and leave them without even the structures that had replace the original ones.
In current Iraq and Afghanistan the US at least try to make sure that there is some kind of stable regime before they leave. Of course it might have been better to not invade in the first place, but since they did, it is their responsibility to try to make sure that some kind of civilian society have a chance when they leave.