Politically Correct Racial Terms

If blacks are called african-americans, then why aren’t:

whites called euorpean-americans;
mexicans called central-american-americans, or better yet, spanish-central-american-americans;
brazilians – portuguese-south-american-americans;

Maybe mexicans should be called spanish-americans, instead of latinos?
Canadians should be called French-Americans.

Since we do not want to discriminate against any certain country, mexicans could be called european-native-americans.

What about people of mixed race? I am Scottish and English. Should I be called Scottish-British-American?