From what I've read on this, in the US a lot of people don't have IDs and it's not obligatory to own one. So how do they ensure the customer purchasing alcohol is of age? Are there any penalties for shops that sell alcohol to kids?
Here in Poland, and probably in the neighboring countries to, the shop clerk will ask for an ID to make sure the person is an adult and can legally purchase alcohol and energy drinks. Should the customer fail to show an ID, the shop will refuse to sell alcohol.