Final answer:
Irish Americans have significantly assimilated into the dominant culture, leading to less visible ethnic markers compared to groups like Hispanic Americans who maintain strong cultural connections.
Step-by-step explanation:
Among the groups listed, Irish Americans have seen a significant decline in visible ethnic markings, such as language and residential clustering. This phenomenon is attributed to a gradual assimilation into the dominant culture in the United States. Over generations, many Irish Americans have intermarried and integrated with other groups, leading to a dilution of distinct ethnic characteristics. In contrast to this, groups like Asian Americans are often referred to as the "model minority," experiencing visibility due to continued success in various sectors but also facing distinct stereotypes. Hispanic Americans, while becoming the largest minority group, have a strong Spanish-language media presence and maintain cultural ties. Consequently, visible ethnic characteristics remain relatively pronounced for Hispanic Americans and other minority groups.