Even beyond his idiotic statement, he doesn't know history. Liberia was America's only colonized nation and was founded by the American Colonist Society in part to give freed slaves the option to return to make a new life for themselves. It was not created from slavery, it was created from emancipation. They created their Constitution based on ours and even named their capitol after President Monroe.
This doesn't change how stupid his statement is. The history has nothing to do with the health and safety of America and the world right now.