This Buzzfeed article– Welcome to America–Now Spy on Your Friends — describes how the FBI routinely interferes with the immigration process in order to exert pressure on immigrants from Muslim countries to provide information. As the article puts it, “[w]hen Muslim immigrants apply to become citizens, they often find the process delayed for years without explanation. Then, when they are at wit’s end, they get a visit from the FBI, with an offer they don’t dare refuse.”
See also this 2013 ACLU report, Muslims Need Not Apply.