When, exactly, did nationalism become synonymous with racism?

Working together for peace .love and racial understanding

Sports writer who said he was uncomfortable with a Japanese winning the Indianapolis 500 on Memorial Day is fired for "racist" remarks. He was referring to a native of a country that we were once attacked by and went to war with (we won, for you younger readers), a war his father fought in. I understand it's been a while since that happened, and I personally have no animus against the Japanese - quite the contrary, but he isn't complaining about a Japanese-American, but a citizen of japan.

I understand that since Trump appeared on the scene, his nationalistic, "America first" slogan has been declared "racist", but it seems to me the switch began before that. I'm just curious when that happened. The country that enjoyed the WWII movies and TV shows ("Combat!") of the 60s had no problem seeing a difference, but somewhere along the line sensitivities changed - maybe the Viet Nam war?

Just idle musing here: the reporter was dumb to say what he did, and he's paid the price, but it did strike me as interesting, on a slow news day.