The USA is the most popular destination for migrants from all over the world. The reason for that is that it is a wealthy country that offers a lot of opportunities in life, it is stable, and relatively safe.
The migrants can cause both positive and negative economic effects.
The positive effects can be seen if the migration is strictly controlled, thus only people with certain skills that are needed in the country are allowed to move in. In this way, the migrants will improve certain sectors in the country, resulting in positive economic effect.
Negative economic effect can be seen mostly by the illegal migrants. These people do not have documentation, work for less money, thus taking jobs away from the legal citizens of the country, and also send the majority of the money back home from the country of origin, the end result being negative economic effect.