This is most definitely a comprehensive list of all cultural differences between Argentina and the US (that I've noticed so far)

1. Dinner is much later

This is true in many Latin American countries. While in the US my family likes to eat earlier than usual (6:30, usually), my host family likes to eat later than usual. 10:00 is pretty normal here, but we eat between 11-12. But it's always delicious.

2. Ways of greeting people

While in the US handshakes are common ways of greeting new people, here, people greet each other with a kiss on the cheek (except between guys who aren't familiar with each other, in which case a handshake suffices).

3. School schedules

In the US, school usually goes from around 8-9am to 3-4pm. Here, school is split into two schedules. Half of the students attend in the morning, while the other half attends in the afternoon. I am in the afternoon half, so my classes start at 1:30 and go to 7:30 most days. Also, we have a short recreo (recess) in between each subject.

4. Students and Teachers

The biggest difference is that students stay in the same classroom for the whole day, and the teachers move between them. School is also much more laid back, and the students hold most of the responsibility for learning. Meaning that teachers don't scold students when they don't pay attention in class or fail to do their homework. Which is nice sometimes, but also frustrating when you aren't used to it. I often don't feel motivated to do the work in class.

5. Drinking and Smoking

The legal drinking age in Argentina is 18, but it is very loosely enforced. Vendors do not require you to show ID, and most parents are aware of and okay with their children drinking. Cigarettes are also much more popular here among young people, and there are often teenagers smoking in or around clubs. 

6. Clubbing

On weekends, teens often go to clubs (called boliches) where dancing starts around 12-1am and goes to around 6am. Before heading to the boliche, groups of friends get together at a previa held at someone's house, where the alcohol is cheaper. There's also conversation and music. When everyone is ready, they get a ride from a parent or from a taxi to the club. Drinks are served at the bar, and there is usually a staff member selling cigarettes. When everyone is finally worn out, kids get driven home by a taxi or a parent to sleep.

7. FOOD

OMG ITS SO GOOD (see my other post on it if you haven't already)

8. Seatbelts

Seatbelts aren't typically worn unless it's a longer drive than usual, despite the fact that there are a lot of crazy drivers here.

9. Carrying Valuables

Pickpocketing has increased in recent years, and for that reason, Argentines only carry small amounts of money at any given time. If you are planning on going shopping, you would bring more. In addition, it's unsafe to walk around town with your phone in your hand.

10. Mate

Mate is a traditional South American drink, served from a special gourd. It's prepared by steeping yerba (herb) in hot water. It's typically passed around within a group of friends and is a common pastime for people of all ages.