Mexican Americans came to the U.S. because of war witch is a political reason for coming. some cultural contributions that they brought were tortillas, tamales and bunuelos.
Italians came to the U.S because they planned to make money and return to Italy. Or they had farm land they did not own. This is an economic reason. also the cultural cotributions they brought were honoring saints and Virgin Mary.
The Russians cultural contributions were traditional dances, and long joyous weddings. The reason they came was the Czars. They were the rulers of Russia. This is a political reason.