I just used this in another posting. I thought it would be worth explaining. I like to mention real idioms that I know are really used.

A quilt is a kind of warm blanket. It looks puffy. It is usually made of two thin layers of fabric with an insulating layer of "down" (feathers).

Quilt-making was an American folk art tradition. Women made their own quilts. Sometimes they got together in groups called "quilting bees" to make them. 

Quilts were often made out of square pieces of fabric, sewed together. That is called a "patchwork quilt."

When the pieces of fabric are all different sizes and shapes, that is a "crazy quilt." Despite the name "crazy," they are often dramatic and elegant designs. This is an image of one:

<a href="https://upload.wikimedia.org/wikipedia/commons/thumb/a/ac/Tamar_Horton_Harris_North_%E2%80%93_Quilt_%28or_decorative_throw%29%2C_Crazy_pattern.jpg/606px-Tamar_Horton_Harris_North_%E2%80%93_Quilt_%28or_decorative_throw%29%2C_Crazy_pattern.jpg" style="color: rgb(17, 85, 204); font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">A crazy quilt made in 1887</a>

By extension, a "crazy quilt" can also mean some kind of complicated system that wasn't fully planned out. It has different pieces. They don't quite fit. They are disorderly. I called the Boston public transportation a crazy quilt because it is a mixture of four different partly-connected subways, trains, and busses.

In a way, the idiom means something different from the real phrase, because the idiom refers to systems that are crazy and disorganized, whereas real crazy quilts actually are elegant and beautiful.

The United States is a federal republic of fifty partly-autonomous states. You could call the United States a "crazy quilt!" Sometimes it seems truly crazy, in the sense of insane. Other times it seems like a folk-art masterpiece.