So far as picture 1 is concerned I can so no similarity whatsoever, other than that they both show groups of men with their faces blacked up. The costumes are entirely different. The way they are blacked up is also entirely different - the minstrels are in true 'blackface' with no white skin showing but with exaggerated lips and eyes, the morris have only their faces blacked but their necks and hands are not.

In the second picture the photo of the morris dancer is too poor to really show what he is wearing, but what I can see bears no similarity to the Jim Crow costume. Certainly the tatter jackets of the Shropshire Bedlams and their imitators are quite different.

So far as we know (and I accept the evidence is scanty) Border Morris has a long history of blacking up. Some of that history coincided with a period when blackface minstrelsy was a huge part of popular culture. It would be naive to imagine that it cannot have had some influence on morris during that period, but that is not to say that the practice of blacking up came from minstrelsy, and nothing else in morris suggests that it is imitating black culture whether real or stereotypical

Minstrelsy thankfully is dead and buried. Morris has moved on. In today's society it would be quite wrong to black up to imitate, let alone denigrate, black people but that is not what morris is doing.