Drownable-in-a-bathtub is too small for any reasonable national government, but setting that aside…

How perceptive.

That the dominant hegemony is a democratic republic founded on liberal and enlightenment values, human rights, and democracy as ideology has some advantages.  For instance, it likely plays a part in just about every autocrat having to pretend to democratic legitimacy.  But those advantages are pretty intangible, so we’ll set those aside as well.

And let’s assume a breakup of Russia and India as well.

Sometimes I oppose things not just because I disagree with them on values, but because I think they won’t even work for the stated goal.  (Doesn’t everyone?)  So a lot of the opposition to American power wants to supplant America with Communism, or Anarchism, or smash it to bits, or dissolve it into global capitalism, or install a world government.

And while often this is based on ideological values about how people should live,

it’s also based on “OH FUCK GEORGE BUSH COULD JUST RANDOMLY INVADE SOMEWHERE AND NO ONE COULD STOP HIM.”

But while knowledge is knowing that America has hegemonic power, wisdom is knowing that that level of relative power isn’t entirely unique to America.  

So not only will those ideas, like turning America Communist, be undesirable in themselves, but they will fail to actually abolish hegemony.  They won’t even work for that stated purpose that was supposed to justify such a radical course of action.

For someone like me, this is a terrible deal.

So as long as anyone else has a continent-spanning superstate, I and the other American nationalists have no reason to dismantle ours.

But this question posits that a breakup of the other 9 million square kilometer nations has already happened.

At that point, I don’t really need a continent-spanning superstate.  It has certain advantages, but the pressing need, to avoid living under someone else’s hegemony, is gone.

And I’m willing to make weird ideological trades.  (I may be a lot less pro-immigration than most of the ratsphere, for instance, but there are conditions where I’d be willing to add all of Mexico to the United States.)

It may surprise you to learn this, but I’ve periodically thought about breaking the United States into a new level of “Regional Federalism” to deal with the increased political polarization.  It wouldn’t work as well as we might like for that, due to the primary divide being urban/rural, so some other designs might have to be investigated, but I’m not as opposed to the idea as some readers may expect.

So let’s suppose we take the idea of a North American Union.  There’s a sort of slider on a continuum of being more like a unified central government towards being a bunch of barely-connected separate nations.  We’ll put the slider more towards the latter.

The American states are too small to be effective countries in the way that we’d like, and many of them are landlocked - very unfair!  So we break America into 3-6 countries, based on the regions.  Each one has some coastline of its own (if 3-4 countries), or else, through the NAU, the Great Lakes Region gets prenegotiated access to the sea.  

This gives us a group of countries which each have a power level somewhere between that of France and that of Japan.  

Minimum military development spending is pegged by the NAU to some % of the GDP and is shared between all of them.  Actual militaries are individual to each country.  There is a mandatory mutual defense pact, and a military coordination center, but pre-emptive wars and the like are optional.  If Texas decides to invade Iran, New York does not have to pay for it.  Outside of this, minimum military % GDP spending is tagged to 2.5%, and NAU members can sue each other if they fail to meet it.

The US Dollar is not abolished, but becomes a basket currency based on the currencies of each of the new NAU member countries.  New currencies are issued for the new countries so that their economies don’t have currency problems like the EU does.

The official language of the NAU is American English.  Proficiency in English must be taught in every NAU member country.  There is no prohibition on adding other languages at the member country level.

The Bill of Rights is kept.

Other than this, since we’re looking for a dismantling, the power of the NAU government is pretty limited.  The number of representatives for each member country is not proportional to population.

For the individual countries, I think multi-party parliamentary systems might result in a bit less infuriating dipolar partisanship.  However, to be more decisive, each should have a President elected by Approval Voting.

That’s all pretty radical, and it’s more of a rough sketch than anything, but I am willing to make ideological trades with people that are primarily anti-nationalist because of things like the Iraq War - they’re just trades that no one can realistically offer.

Then again, by the mid-century, who knows?