The Marc Jacobs line sunglasses are made in Italy, but the Marc by Marc Jacobs line is made in China and the same with some of the mbmj purses and clothes. I don't know whether your marc Jacobs is real, but if it was from a department store or the official Marc Jacobs store then its definitely real, but if it was from a pair of sunglasses stand or a small store that isn't very known then it is probably fake. But Marc by Marc Jacobs glasses are made in China.
No, you can not say all the marc Jacobs sunglasses are made in china. Actually, there are many types that are made in china, while there are also many other types which are made in Italy or some other places. So if you want distinguish them, it's very difficult to judge them just by the label which can be 'made in china' or 'made in Italy'. In my opinion, you can take them a sunglasses store and ask the authenticity guide to give you professional guide.
Just like the brands Nike, Addidas and so on, the marc jacobs company which main company is located in America has its own several branches in China and other places around the world. And the branch companies are mainly responsible for the manufacture. About the design, it is the American company takes the responsibility.