Yes it has. Going by the Wikipedia definition of racism:
https://en.wikipedia.org/wiki/Racism
Kids having a good time doesn't fall under these points.
As someone mentioned before, there are multiple example of different standards in different cultures.
Things that might be offensive in the US might not be offensive elsewhere and vice versa.
Even usuing the term "race"(Rasse) in connection with humans is not acceptable in germany.
In the US its no problem.
But no german would go ahead and say americans who are usuing the term race when they refer to different ethnicity are per se racist.
In germany when you speak of race you're are quickly called a nazi.
The term just has a lot of history in germany, just like blackfacing has a history in the US.
But in the US the only history the term has is as a synonym for ethnicity, and the only history blackfacing has in germany and the netherlands are some weird christian tranditions or dressing up as famous cartoon characters.*
*I don't know if Jim Knopf is known outside of germany. But the depiction is highly questionable, yet he is a hero for many kids and they want to dress up like him.(At least back in my days.)