How do political pressures influence language change?
I'm not exactly sure what you are looking for with this question, but taken literally, often times a society (like the United States) is resistant to the influence of new and foreign languages. Immigrants moving from Germany or Poland in the early 1900s, for example, often lived in "enclaves", small cities and neighborhoods where they could find acceptance together with their own culture and language.
So perhaps the biggest influence of politics on language is that pressure from the dominant culture can limit what is taught in the public education system, or the language of official documents, such that the dominant language (English) most likely remains so over time. This doesn't stop words from the new languages from making their way into the daily language of everyone though (words like Kindergarten and Gracias, for example).