There's actually nothing wrong with the costume, it's a clever combination of Osaka 'gal' style with stereotypical American Indian motifs. But it's smart of them to change it given the backlash that would happen in the US if it were left as is, as too many people will see it as an attack on a marginalized social monitory.
It being replaced by 'cowboy' is pretty inconsequential, in this case. The overall aesthetic doesn't have to change much since it's still mostly brown leathers, and Cowboys fit into the same 'Cowboys and Indians' era of Americana and can use rifles as well. All in all a good decision but I'm happy to have the original version, I'm never thrilled about content being modified for different regions, regardless of how it was changed.