False. He claimed that the states declared independence from Great Britain as a single nation.
In reality, meanwhile, the Declaration of Independence did not declare the states to be a single nation, but several, in the Declaration of Independence:
So each state was individually declared as a sovereign nation to itself, and they mutually recognized each other as such And they likewise secured this status as their express intention, under Article II of the Articles of Confederation in 1781:
However, this was still simply a declared status that was mutually recognized among the states, which were still officially colonies of Great Britain at that point under international law.
Each state only became an official sovereign nation under international law, when recognized by Great Britain and other nations of Europe, in the the 1783 Treaty of Paris:
And this made them officially into sovereign nations.
Accordingly, the American states remain separate nations, by law; the People of the state remain the supreme rulers thereof— as Madison writes, “derived from the supreme authority in each State, the authority of the people themselves… The states, then, being the parties to the constitutional compact, and in their sovereign capacity, it follows of necessity that there can be no tribunal, above their authority, to decide, in the last resort, whether the compact made by them be violated; and consequently, that, as the parties to it, they must themselves decide, in the last resort, such questions as may be of sufficient magnitude to require their interposition (The Virginia Report).”
So the registered voters in each state, can overrule any legal by on Earth by popular vote in state convention— just like the UK could overrule the EU in Brexit, and as the Peoples of each state did in 1787-9