Both of these countries are multi-ethnic, great powers, with very diverse groups in their societies. Both groups are known for direct and blunt speaking. These two cultures most likely belong to --

These two cultures probably belong to the American continent.

Explanation:

Although the most multiethnic continent in the world is Africa, America is a very multiethnic continent with two countries considered to be world powers (USA and Canada). The American continent has this rich and ethnic diversity because it was home to several peoples, even before the arrival of Europeans, the continent had hundreds of indigenous tribes and other civilizations such as Incas, calchaquíes, tzotziles, Olmecas, Mayans, Guarani, Tupis etc. With the arrival of Europeans, the continent began to receive people from all over Europe, many people from Africa and the East, generating a highly diversified population.

reflecting point a across the origin negates both of its coordinates.

b = (5, -4)