But it is based on race, just an older definition of race. There was a time when southern Europeans were classified as the "olive race". In the bollocks scientific racist hierarchies of the time, that put them below the Aryans, but above the Semites and the blacks. The Nordicist racists of course considered themselves the apex, and looked down on the rest. In the US you guys still remember how the Irish, the Italians, the Greeks, the Poles, the Jews, were very slowly integrated into the category of White, meaning they were not always considered White.
The caricatures of the lazy southerners are indeed racist stereotypes of this past era and to claim that they do not persist in the modern era is kind of weird, seeing how so many other racist stereotypes persist.
Absolutely.
I would just however push back on the implicit hierarchy in the way you write it, where cultural prejudice is a smaller degree of prejudice compared to racist prejudice. For example, a black American tourist in, say, N. Ireland, will probably face less prejudice than a white Romanian immigrant. It's all intersections.