Assimilation. Used to be that way.
Would you say that part of the culture of the UK is the English language? Even though it was the Angles, Saxons, and Jutes who brought the earliest form of what we call English? Even though the language was assimilated among the Brittons, and even eventually among the Scots of northern Britain? Even though English assimilated a layer of Norman French after William conquered England? And so all the greater literary works, the Canterbury Tales, the works of Shakespeare are the product of an assimilated language--those are still part of English, and even more broadly, British culture?
How about English Common Law practices which were also introduced largely by the Normans following the conquest?
Let's talk about America's own literary traditions, the works of Melville, Twain, or Salinger? Not American culture?
Let's talk about food, Italy is famous for its culinary tradition and food culture, can you think of anything more Italian than a Neapolitan pizza or pasta with a tomato-based sauce? And yet, the tomato is a crop from the Americas. An imported crop that has become not only a major component of the food culture of Italy, but in many of the cultural traditions of Europe. The same is true of the potato, a tuber that originates from the Peruvian Andes.
But let's go back to Italy, we talk about "Italy" as though it were a single nation and we talk about an "Italian culture"--but up until the 1800s Italy didn't exist. The peninsula was for centuries a patchwork of states, the Pope ruled the Papal States from Rome (Vatican City is the vestige of the old Papal States), and there were the famous city-states of Florence, Genoa, Venice, with unique traditions all their own. And before the rise of the Italian city-states, before Charlemagne's conquest, there was the Kingdom of the Lombards, one of the Germanic states that appeared during the Migration period, where after the fall of Rome the Germanic tribal nations settled and established their own kingdoms throughout Western Europe--the Kingdom of the Franks, the Kingdom of the Lombards, the Kingdom of the Visigoths. And all these kingdoms and peoples settled and assimilated into the local populations, influencing language, local laws, creating amalgamations of culture; forging cultural developments out of the old Roman cultural traditions which had dominated in these regions with new and foreign traditions introduced by these migratory and now settled tribes.
Go anywhere and you'll find these same historical forces at work. Every village, every region, every modern state, a long history of amalgamation, assimilation, cultural exchange. It's everywhere.
So unless your argument is that culture doesn't exist at all anywhere, for anyone, then your rebuttal is meaningless faff.
-CryptoLutheran