I think the argument is a bad one, and also that this and many other arguments Mitch McConnell makes are made in bad faith (though not all). The most obvious reason this argument is not compelling is we don’t have a counterfactual to see at what rate Black Americans would vote if they had as much easy access to ballots as others do.
But I also think that his statement here is neither a justification of disenfranchisement nor is it a suggestion that the real Americans are white. It’s a moderately awkwardly worded statement that has one obvious interpretation that is a fairly straightforward claim.
Yes, that’s what he was doing. Since the last election, especially in Georgia, Florida, and Texas (especially Georgia), laws have been passed that will make it harder for African Americans to vote. This was done on purpose, because the Republicans were blindsided by the loss of both senate seats in Georgia.
The Senate was trying to pass several election laws that would make it harder to pass the kinds of laws that those states passed, so the Senate was trying to prevent the current and future disenfranchisement of African Americans. McConnell was against those bills, and pointed to the past, where the new Georgia (etc.) laws hadn’t passed yet.
So, he was saying that in order to justify voting against bills that were trying to prevent the disenfranchisement of African Americans.
Blacks aren’t real Americans, that’s what he meant. It was a Freudian slip. Pence made a similar slip previously. The GOP is a white supremacist movement, hence the fascist game show host that leads their party.