You don't see how my point is valid because, to put it bluntly, you don't appear to have a great understanding of history.
The Roman expansion began against the Etruscan city states, not Gaul. In both cases, Etruscan and Gallic people were brought into all spectrums of Roman society, including the military and Senate class. The period of rapid progress in the Roman Empire was largely a result of incorporating foreign culture and technology. They were one of the most multi-cultural Empires the world had ever seen; perhaps only exceeded by the Arabic Empire I also mentioned.
I have no idea how not conquering Scotland or the Sahara are relevant to anything, you'll have to explain that one further.
The US "Golden Age" - as you call it - had nothing to do with xenophobia, and everything to do with the rise of social welfare policy under FDR to revitalize the working class. In fact, quite the opposite trends were occurring: the downfall of segregation, a rapid expansion of immigration, the incorporation of minorities into the working class, and the opening up of the US into partnerships with nations around the world; in part, to fight AGAINST the xenophobic powers in the very war you mentioned. There was temporary Xenophobia against Japanese, but this is largely explained by the fact that the US was at war with Japan, and the actions were largely seen as embarrassing and regretful - held as an example of something the US did wrong in that time period.
The Roman expansion began against the Etruscan city states, not Gaul. In both cases, Etruscan and Gallic people were brought into all spectrums of Roman society, including the military and Senate class. The period of rapid progress in the Roman Empire was largely a result of incorporating foreign culture and technology. They were one of the most multi-cultural Empires the world had ever seen; perhaps only exceeded by the Arabic Empire I also mentioned.
I have no idea how not conquering Scotland or the Sahara are relevant to anything, you'll have to explain that one further.
The US "Golden Age" - as you call it - had nothing to do with xenophobia, and everything to do with the rise of social welfare policy under FDR to revitalize the working class. In fact, quite the opposite trends were occurring: the downfall of segregation, a rapid expansion of immigration, the incorporation of minorities into the working class, and the opening up of the US into partnerships with nations around the world; in part, to fight AGAINST the xenophobic powers in the very war you mentioned. There was temporary Xenophobia against Japanese, but this is largely explained by the fact that the US was at war with Japan, and the actions were largely seen as embarrassing and regretful - held as an example of something the US did wrong in that time period.
Before gauls were, per your words, "brought in" they were slaughtered and enslaved en masse... Julius boasted about killing a million of them and enslaving as many, considerable numbers in those days..... This did not seem to phaze the roman elite at all...
As for the great roman tolerance you may ask the jews and others (delenda est Carthago!) who were victims of genocide and ethnic cleansing.... The romans were not so accepting of differences, but they would accept those who "romanized" on their terms
Temporary xenophobia in the US against the japanese ? Only ? that conveniently forgets the mexicans (who were ethnically cleansed including during the first FDR presidency), the latin americans in general, the chinese and of course african americans and indians to name just a few... There was nothing temporary about that, it lasted for the most part of the US existence.... Who are we kidding here ?