Ameliorate the Melting Pot

Directions: students should ameliorate the sentence below, in red.  There are two missing commas.

The melting pot theory popular in the late 1800s U.S.A. was that many different cultures will melt together into one homogeneous group with shared values.

Suggested Answer: 
The melting pot theory, popular in the late 1800s U.S.A., was that many different cultures will melt together into one homogeneous group with shared values.