For me Trump's wall is not different from the other two, because according to him the wall is used for defensive and preventive purposes. He wants to expand the wall to avoid drug trafficking from Mexico.
The Berlin's wall was built for political reasons while the China wall was built for defensive reasons.
Trump's wall wouldn't back migratory flows to people who have difficulty and could not reach the U.S.A and this is a bad thing because the people can't have a beautiful life and they are forced to live in difficult situations.
The walls are used to build buildings, not to divide thousands of families and prevent migrants from having a better future in a different country.
in conclusion I think that the Berlin Wall and Trump'S Wall only serve to destroy, while the Great Wall of China at the time it served to defend the state and now it has also become a tourist attraction for its splendor.