The United States has participated in at least two genocides, Africans and Native Americans. Both of these were politically supported primarily by the Democrats. Andrew Jackson used a donkey to represent that he was too stubborn to be swayed by abolitionists or those advocating for Native Americans. The Democrats still use that symbol.
It is very much like having the NAZI party around. During WW2 the Democrats controlled the government and rounded up ethnic people, Japanese, German, Italian, and put them in camps. I don't know exactly how many died during that round up, but, genocide is defined by targeting and killing people based on ethnicity. I don't think there is a specific number attached.
Although, calling the rounding up of people and causing the death of, hundreds, thousands, A genocide does seem to detract from the genocides of Africans, Native Americans and Jews....