Earlier quoted context omitted.
Or it's extremely basic text matching and "African American Inventors" more closely matches "American Inventors" (as it is an exact substring match) than web pages about "Inventors from the United States", which is probably a more common phrasing (see: https://www.google.com/search?q=Inventors+from+the+United+St... ) One of the biggest problems with Google as I see it, and facebook for that matter, is for the end use…
I added more search terms. Here are the results for "white inventor" on Google Images for example. https://www.google.com/search?q=white+inventor&tbm=isch
It's pretty common for certain words in certain image searches to be useless, and that's including a lot of very boring searches nobody has ever thought of.