Besides family and friends? For me, good ethnic food, high quality fish, cheap consumer products, the weather and ocean in California, garbage disposals, dryers, reliable power and internet, ease of traveling by plane domestically, ease of buying/leasing a car, ease of renting an apartment/picking up and moving, uber-friendliness and desire to help by random, trusting strangers. That said, living in Buenos Aires seems in most other ways far superior to the U.S.