I don’t want to defend the Louisiana Purchase or the Virginia Plan, but let’s not drop the context: the LP was not only an act of expansion, it was also the peaceful removal of an imperial foreign power from America’s doorstep. Madison’s notion of giving the federal government a veto over state legislation, an idea frequently invoked to show his centralizing desires, was more about diffusing power than concentrating it. History has disproved Madison’s belief that power is more diffuse in a large republic than in small states, but he certainly was not trying to create a consolidated nation state. Madisonian federalism, although not decentralized enough for my taste, is not nationalism.

Context is also important in discussing nationalism. Was John Bright a “nationalist” because he supported Home Rule for Ireland and greater autonomy for India? Because, that is, he loved Little England (a nation) rather than the British Empire (not a nation)? The commitment of many classical liberals to nationalism in the abstract arose from opposition to empire. After World War I, that commitment became problematic, but by then classical liberalism was on its deathbed. In any case, there had always been classical liberals who did not embrace nationalism.

Lord Acton and Alexis de Tocqueville are by-products of 20th century American politics?

I would suggest that James Madison and Thomas Jefferson are more probable sources of the American conjunction of decentralism and classical liberalism than “exiled liberals from central Europe.” (I presume you mean 20th-century Austrian emigres such as Mises and Hayek.) Madison and Jefferson were both flagrantly inconsistent in their decentralism, but to be an inconsistent decentralist is not the same as to be a committed centralizer. Of course, many of the exiled liberals who came to the U.S. in the wake of the 1848 revolutions were exactly the kind of national liberals you criticize. They reinforced the centralizing tendencies that had developed over time from the National Republicans and Whigs and thereby helped nationalist liberalism win out over decentralist liberalism in late 19th-century America. But the tradition of American decentralist liberalism did not vanish — at the very least it remained available as a rhetorical weapon for anyone who opposed National Republican/Whig/GOP centralizers.

Classical liberalism had different strains, some of which were highly centralist and some of which were decentralist. The centralizers generally prevailed in government — just as centralizing non-liberals (like Bismarck) generally prevailed over decentralist non-liberals. This is where the term “statist” might be quite useful: there are classical liberals, traditionalists, and socialists who are in favor of enlarging the central state to accomplish their objectives. There are also classical liberals, traditionalists, and socialists (of the Bakunin variety, for example) who are opposed to centralized state power even when it might be used to further their own agendas, or who believe that large centralized government’s are inherently inimical to those agendas.

Political philosophies and ideologies are easily appropriated by political parties and governments. Hence to call a politician a conservative or a liberal may reveal very little about his actual policies. But “statist” is a more content-laden term than conservative, liberal, or socialist. That doesn’t mean that centralizers and aggrandizers of state power won’t try to criticize statism and position themselves as anti-statists, but the term, because it is relatively concrete, makes it easier to expose them as frauds. Your post is an illustration of this point: because statism is predicated on something concrete, you can show that so-called anti-statists are not actually against expanding State power or using it aggressively.

One can argue that the conservative movement is not conservative and that modern liberalism is not liberal, but there’s more abstraction and contingency involved in fighting those fights than there is in showing that, say, Republican critics of “statism” are not really arguing for a smaller State. That doesn’t mean “antistatist” can’t be appropriated, but then any term can be appropriated by political actors. There’s something to be gained, though, in making the appropriation as awkward and incongruous as possible.