A tariff on aluminum will only do two things:
-Force companies to use plastic instead of aluminum if they are to avoid the tariff.
-Pass the costs of the tariffs off to the consumer. That means we will end up paying more for things made of aluminum.
One thing that the tariffs are NOT doing is making it so that more things are being made in the United States. For example, the iPhone has a lot of components that are readily available in China but not the United States. It would still be cheaper for Apple to pay a tariff than it would be for them to move their manufacturing back to the United States.
Acer, ASUS, and Samsung are not based in the United States and have no reason to manufacture in the United States, but will still have to pay our tariff on aluminum. They would still need to either switch to plastic or hike prices on their aluminum products, even though there's nothing they could do about it.