Some US States are working to turn this around and have introduced [edit to finish thought: bills to change it]. It will take a while. Given that many states used felony charges and laws that don't allow felons to vote to control minorities, it may take a long while indeed.

Wikipedia actually has an interesting map on the subject for the US (below the fold/ToC):

https://en.wikipedia.org/wiki/Felony_disenfranchisement