I understand in application it only applies (for the most part) to US citizens. But by saying that gun ownership, and all weapons ownership, is an inalienable right - then our government (as the actor) should not take any action infringing on any person's (citizen or not) of owning any arms. If nukes are included, then any individual should have the right to bear nukes.
In your hypothetical - our government should not do anything to PREVENT a republic from forming. These rights prevent the government from taking action, not requiring affirmative action.
If it applies to everyone, we can overthrow Castro, the Iranian mullahs and the Chinese Communists tomorrow.
And we didn't need any reason to oust Saddam. It's right there in the Constitution.
If the 2nd applies to everyone on earth, so does it require the U.S. Government to provide everyone on earth with a republican form of government.
Or maybe it just applies to U.S. citizens and it takes an act of the Congress to authorize taking on a foreign country.
You don't get to pick and choose which parts of the Constitution you get to enforce.