Nonsense reductionism. France and Germany maintain separate cultures despite having a shared open border. Philadelphia and Pittsburg have different cultures despite being in the same US state.

The difference between Globalism and Nationalism is that Nationalism hides behind arbitrary borders and trade taxation, to protect some temporary resource amongst it's internal, often Democratic majority, refusing to yield it to the efficient Global free market.

All Nationalist states are short-lived because there is no long-term benefit to nationalism. "Strong borders" are a waste of money in a prosperous world. An economic net-negative. If France and Germany ever militarized their borders again, no positive economic or social benefit could come from it.