People migrated to the US for many reasons, one of which was to find religious freedom. In many other countries they will hold you to a specific religion, otherwise you had no freedom. Another reason people migrated to the US is because where they were before there may have been poverty, in the US you have greater opportunity to prosper or at least make a livable income to sustain yourself. As for challenges immigrants and even refugees face many issues. An example is that Syrian refugees are in a war torn country with many terrorists ruling over them. Another major issue is that some immigrants illegal or not have trouble adapting to our society or even have trouble with English.