https://www.google.com/search?q=american+inventors
https://www.google.com/search?q=american+mathematicians
https://www.google.com/search?q=american+scientists
Image results:
https://www.google.com/search?q=european+art+history&tbm=isc...
One of the biggest problems with Google as I see it, and facebook for that matter, is for the end user there isn't much of a way to introspect _why_ a search result comes from a particular query. In this case, you used that lack of information to confirm your own assumptions and bias.
This situation is a good example of why it's important to pay attention to maintaining the appearance of impartiality as well as actually being impartial.
(Disclaimer: I work for Google. Nothing related to search.)
This is one of the social dangers of allowing algorithms to make important decisions in society. We might not even be aware of what biases we're introducing. They can be very non-obvious, especially if the algorithm is complex or the data set is large.
Edit: here's another possible explanation: perhaps due to efforts to popularize African American contributions to American history there are more web pages (in a pure numeric sense) about African American inventors, scientists, etc. on the web. This could affect the way Google weights search results.
This isn't a danger of AI in the future, it's a danger of google's algorithms in the present. Most users (myself included) have come to treat Google results as some oracle of truth, so the bias introduced by Google's existing search algorithms can have tremendous impact. Most of the time it will go unnoticed, and it doesn't require any intentional manipulation. What people know, and how they act based on what they know, is being heavily influenced already by google's algorithms.
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.
This would seem to both belie the claim that it is manipulating the results -- by virtue of the fact that wouldn't the first thing they manipulate away be this very criticism -- and seriously taint the chain of events that led you to claim that they are.
https://en.wikipedia.org/wiki/Category:American_inventors
There is a sub category called "African American inventors". Since the sub category also match the search terms, it is possible that for some reason they are displayed in priority.
edit : the post of econ4all about "us+inventor" tend to confirm that it is an issue with "american" being part of "african american"