I'm supposed to teach a class tomorrow. My first ever. Unfortunately, I've never studied grammar and I've suddenly found myself in hell.

I'm having trouble with the following:

1) Baseball is the national sport of the United States.
2) The national sport of the United States is baseball.

In (1), baseball is the subject, right? But in (2), is baseball still the subject? Or is the subject now the national sport of the United States?

What's the object? Is there an object? If so, is it direct or indirect? Why?

Luckily I'm not supposed to be explaining any of this tomorrow, but I do need to get it clear in my head. Obviously.

Help!