American-style mozzarella comes in blocks or pre-shredded bags, looks like a pale yellow cheddar and has a rubbery texture.
It looks like provolone, and is actually more similar to scamorza cheese than it is to genuine Italian mozzarella.
Though it can be eaten fresh in theory, it is almost always used as a cooking cheese, in particular as a pizza topping.
It is the “default” mozzarella cheese in both the United States and Canada. If someone asks you to get mozzarella cheese for them from a supermarket, this is the cheese most people would expect you to buy.
Use the American-style mozzarella for cooking.
2 cups grated / shredded American-style mozzarella ≈ 8 oz. / 225 g in weight
7 oz. / 200 g American-style mozzarella, diced ≈ 1 cup
12 slices American-style mozzarella ≈ 8 oz. / 225 g
American-style mozzarella freezes well for use in cooking later.
You can shred it first, pack it into freezer bags, and then freeze. As it freezes, you may want to massage the bag to help avoid it freezing in one big lump (or, freeze it first on a cooking sheet, if your freezer has room for this).
Over time, though, it may form one big lump anyway. Use a serrated-edge knife such as a bread knife to saw off a portion that you want to use, and put the rest back in the freezer. Let the portion you cut off thaw a bit for a few minutes, then crumble it by hand.
It is fine for most cooking applications to use the shreds still partially or mostly frozen.