What are the possible consequences, for pirating (movies), for a teenager?

[Archiee]

No need to be hypothetical. That's the beauty of written law.

Pirating movies, songs, books, video games, or other Intellectual Property is treated under the same set of laws.

If you get caught, the US government provides statutory damages of $750 up to $30,000 per work (per movie that you're pirating)... unless the copyright owner can prove that you did it willfully (they probably can), in which case the statutory maximum raises to $150,000 per movie. Copyright Law: Chapter 5

Now, those are the statutory damages, they copyright owner could chose instead to go after you for actual damages. That's means that the court can order you to pay whatever the copyright owner lost, plus any profits you made. They'll probably content themselves with the statutory $150,000 per work.

You can also go to jail if your violation is criminal. The maximum sentences run from as short as 1 year to as long as 10 years depending on what exactly your violation was. 18 U.S. Code § 2319 - Criminal infringement of a copyright

"But, I'm a hypothetical teenager!" you cry. While I was researching the exact legal codes, I noticed that in common law, children over 7 are often held accountable for their own torts, so in many places, as a teenager, you may end up directly responsible. And in many states, you can be tried as an adult after age 14 if your crime justifies it.

In California specifically, your parents or guardians may be held financially responsible for the damages, even if the courts won't make you pay. That's under California Civil Code - Section 1714.1 Law section but your parents would probably be limited to $25,000 per movie you pirated. 

One other note, countries that have signed the Berne convention and other Copyright conventions (essentially the UN Member States and the Holy See) protect each other's Artistic Works under the laws of the Author's Country. So if you provided pirated films to someone from Argentina, they could be tried under US law, and if you downloaded a movie from Azerbaijan, you could be tried under Azerbaijani law.