The problem that you're not considering is that they don't have a country. They are refugees who have been driven from their country by insurgents or terrorists etc and in the case of South Sudanese they have come from refugee camps in other countries before coming here. The majority have been sitting in hellish camps for a decade or more. Yes some of their youth are causing a few problems in certain places which has to be addressed, but sending them back to where they came is not an option.
