If you are talking about the 19th century, the strain of liberalism that existed back then was comfortable with nationalism and racialism and was often opposed to monarchy, dynasties and multinational empires. The highly educated used to be fervent nationalists.
If you are talking about the 20th century, the strain of liberalism that became ascendant after the 1920s rejected its predecessor. It championed a strong state led by experts drawing on social science over a weak state pinned down by constitutionalism. It rejected racialism in favor of antiracism. It rejected the Victorian patriarchy, separate spheres and gender roles in favor of feminism. It embraced modernism and cosmopolitanism. It rejected nationalism in favor of globalism. H.G. Wells popularized the concept of the World State. It elevated aesthetic self-expression and self absorption over moralism.
“Sohrab Ahmari wrote a cover story for Commentary in 2016 titled “Illiberalism: The Worldwide Crisis.” In this essay, he mourned the fact that “as an ideology and as a governing philosophy, liberalism is fast losing ground.” In Hungary, Ahmari regretted, Viktor Orbán had “mused about ‘building an illiberal new national state’ on Turkish, Russian, and Chinese blueprints,” driven by a longing “for the return of national will and cohesion — as well as the territories and populations — lost to the cruel 20th century.” …
Today, Ahmari rejects nationalism and liberalism as birds of the same feather. In a recent Compact essay, “The Return of Liberal Nationalism,” Ahmari — in keeping with his latest Marxist-curious turn — recites a version of Eric Hobsbawm’s historical account of nationalism, arguing that “in practice, liberalism and nationalism arose in tandem, beginning in the late 18th century and throughout the 19th.” The marriage of the twin ideologies ruptured after World War II, as “19th-century liberalism’s defense of the nation as the ‘sacred community’ that framed liberal rights” was transplanted by “a cosmopolitan liberalism, in which the empire of rights was to span the whole globe.” (A “sacred community” that gives “concrete shape to our individual rights and identities” — sound familiar?) But today, in the face of Russia’s invasion of Ukraine, Ahmari sees liberalism and nationalism as reuniting …”
The culture war began in the 1920s when Sinclair Lewis published Babbitt.