I do not see a map, so i cannot answer your question
The answer is imperialism.
Assimilation was considered one of the keys to successful imperialism. According to Oxfords dictionary, imperialism is a policy of extending a country's power and influence through diplomacy or military force.
"Diversity, Oppression, and Change" is a social work released by Flavio Marsiglia & Stephen Kulis around 2015; to analyze the diversity issues, achieve positive change, break down the picture of oppression and privilege and help understanding the dynamics of oppression certain social groups have experienced, and therefore attain an unbiased and equitable society. (<em>true</em>)