If they are born in America, depending on the county/municipality they really don't have to speak much english. Many Cajuns speak no english, shall we kick them out? That is not American. Indians are also not required to learn English.
I cannot believe you want to compare the Cajuns to the Russians in Latvia. Let's put it in some context, shall we? 1, the Cajuns are indeed more required to speak English than the Russians in Latvia were required to speak Latvian, at least until the fall of the Soviet Union. 2, the history is entirely different - the Cajuns settled in Louisiana, the Russians were bussed in by Stalin to obliterate Latvia as a nation. 3, the Cajuns do not set up a "Cajun Political Party" to skew Louisiana's politics to their interests - they either become Republicans or Democrats.
If you want to make stupid analogies, do try to get one that does come closer to the mark.
Ivan