The notion of a public good held by liberals extends to all of humanity. They may recognise different cultures and different cultural needs for a legal system separating nations (although they will restrict their respect for alternative frameworks to matters of ethics, commits and preference, hoping for a uniform, if broad, consensus on morals in law), but their alignment to a nation is not to the nation per se - rather to the law and culture as they embody liberal norms. They also have a focus towards the broadest public good, spanning different legal systems (to the extent that this would not reward irresponsible behaviour or "gaming the system") and nations. Liberals are thus internationalist, identify with humanity as a whole more than any nation, and skeptical to hostile towards national separatism.
Likewise, this extends to other nonessential identities - strong ethnic or "people"-type identities are, so much as is feasable, to be discarded if and as tensions and inequalities disappear. The purpose and scope of this is not to create a homogenous society - these allegiances and identities should be retained, at most, so as to create a boutique within a multiethnic society, permitting hybridisation without shame (sometimes called intermarriages), blending and borrowing of traditions, foods, music, holidays, and those values which do not conflict with liberalism, socialism, and secularism. Programmes and institutions which aim to protect acceptable minorities (an example of a not-acceptable one being the KKK) may exist during a transitional period of society. Longer-lasting institutions must be open to society at large and accept blending (e.g. institutions promoting italian culture must not be restricted to italian ethnic membership and must be fully friendly to broad societal values).
The values stated here stand in contrast to some forms of liberalism currently in practice, particularly those tied to Multiculturalist Liberalism. Our form of Liberalism opposes their stance on the issues that divide us.