Congratulations, welcome to America.
The accomodation during the long flight to America is varied, depending on which airlines and which classes you fly. You will not be hungry if you're not too picky with food or drinks unless you must connect with a domestic flight in America.
Generally, overseas flights will offer drink often to keep the passengers hydrated during the flights. All refreshments are free and you can ask for them whenever you need them. You can request special meals, ie. vegetarian or muslim meals at check-in counter. Meals and snacks are usually serve frequently except during sleeping times at night. These meals and snacks are also free of charges. I think if you get hungry or thirsty between scheduled serving times, you shoud be able to ask for extra snack or a drink without any problems but I wouldn't ask for a meal. If you have any medical requirements to eat or drink at certain times, you should pack a litlle snack, but you must discard all fruits and meats before arriving at American custom. If you have to make a connection in America, you will have to pay for food and alcoholic drink on domestic flights but the snack and softdrink are free.
One extra tip, bring warm clothings since you will be arriving in the winter, it will be very cold wherever you land.