As someone who came to the US as a refugee, the differences are far more nuanced than the food you eat or the language you speak. An insular community may legitimately feel threatened by the influx of outsiders. I've witnessed first-hand industries that have been rendered inaccessible to native-born folks through immigration (construction trades). I consider myself lucky to have had the chance to move across continents, but I also think that it's completely natural and rational to keep the door of your home shut to strangers.