What are the similar justifications given for making English a national language, during the last two centuries and today?

The research paper should be conducted on the English-Only Movement. Indicating how the movement was initiated and resulted with language-racism within the United States. The importance of bilingualism should also be signified, especially in the educational context. Finally the paper should be concluded with the argument that there is a necessity for a official common language within a country which can unite the society. If the official English language can be fallowed by a bilingual education system , than US will be able to have a collective identity as a whole, as well as acknowledging the diverse communities that live within.
The overall paper should include answer to the provided questions:
What groups have been the focus of English Only arguments?
How have educators, law-makers, businesses and others tried to limit multilingualism?
What are the similar justifications given for making English a national language, during the last two centuries and today?
What are the differences?