Rhythmless Nation is a slur used to describe Whites in a derogatory way. Refers to the fact that white people cannot dance. Janet Jackson also made an album called "Rhythm Nation" for people with rhythm (not white people).
The word Rhythmless Nation is a racial slur that has been used historically to degrade and dehumanize whites. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to whites. If you are unsure about whether or not it is appropriate to use the word Rhythmless Nation, it is best to err on the side of caution and avoid using it in any situation.