Although I disagree with the use of hyphens to describe someones nationality, lets take the explanation a few steps further.
The use of Asian and African Americans are both used incorrectly. As you know, Asia and Africa are continents. They are not countries, therefore they do not properly name the country in which a person was born. So, if someone was born in a country outside of the USA and later became an American citizen they could hyphenate their nationality. For an example, I'll use Kenya. If a person was born in Kenya, moved to the USA, became a citizen and really wanted to hyphenate, they would be considered a Kenyan-American. The same would be appropriate for anyone born in a country in Asia, born in China, Chinese-American.
Like most Americans, my family tree is ethnically diverse. I'm a ninth generation American and I have ancestors from England, Ireland, Scotland and Germany. If I were to use the rationale of some people that oppose my point of view, I would need to hyphenate as an English, Irish, Scottish, German - American to describe my nationality. I completely disagree with this opinion and would never hyphenate my American nationality.
Recently, I've heard the use of Jewish-American, Arab-American and Muslim-American to again show the differences with Americans. Why are we using a groups religion or a language to incorrectly hyphenate our American nationality? I've never heard anyone describe their nationality as a Catholic-American, Baptist-American, Lutheran-American, Methodist-American, Protestant-American etc. Why divide us and our country even further into more special groups? What's next, Atheist-American, Agnostic-American, Scientologist-American?
I'm in agreement that we should be proud of our heritage and thankful to our ancestors, but I don't think we need to hyphenate our nationality to do so.
Are we the only country that uses hyphens to describe our nationality? I believe we are!
If you were born in the USA, you're a USA NATIVE and you're an American by nationality.
As a nation we need equality for all AMERICANS! Separating us isn't working, let's try something new!