It's very common in the US, at least the parts I've been. It depends on the restaurant, of course, but most places will provide a takeout box to take home uneaten food if you ask.
In fact, it's not uncommon for the waiter to offer a box unprompted if you have a fair amount of leftover food.
In fact, it's not uncommon for the waiter to offer a box unprompted if you have a fair amount of leftover food.