Why is the u. s. population considered a "salad bowl" of homogeneity? because groups have mixed together but have maintained their diversity by retaining cultural differences because most groups are shedding their ethnic culture and shifting towards a unified american culture because cultural differences have not been assimilated even though a mix in ethnicities has been traced in the population because different ethnic groups have mixed together in america and lost their original identity, diversity, and cultural nuances because ethnic and cultural differences have been retained by a lack of mixing between different ethnic groups?