More likely that O’s salesclerk didn’t like Americans. I’ve experienced that when traveling in Europe. Some will come out and tell you to leave and some just ignore you and won’t serve you. I’ve been in some expensive stores there and was totally ignored, but I’ve also been treated really well. Racism had nothing to do with it.
The worst treatment I experienced in Europe was by a taxi driver in Köln, Germany. He was an uninformed, arrogant ass who took advantage of a captive audience (me & the Mrs) and told us what he thought of Americans. His biggest gripe was that the allied bombers had bombed his city (Köln) and killed his grandfather. I told him I thought he was upset because we kicked Germany's ass. With that, he abruptly pulled over and asked us to get out which was fine with us; we were only about 2 blocks from our destination and I didn't pay him so the ride was free. :-)
When I asked him if all those images of the Jews in concentration camps were real he told me not to believe everything I read in our American history books.