I have no idea if there is a standard about when to use "USA" (or expansion thereof) - if there is, I suspect it's fairly localised. That means, I believe, that I have to fall back on logic - perilous!
I don't believe that recognition of independence by Great Britain should be relevant - after all, the danger (in general) is that recognition is not granted. In practical terms, the "colonies" are operating independently before 1784 and GB's recognition, so genealogical sources will be created by the "colonists" on their terms, using their names, and stuff will be filed by those names, i.e. recognition is not relevant, internal usage is. (Of course, if the whole thing had collapsed, it might be a different story, e.g. a potential counterargument to internal usage: does anyone use "CSA"?)
So far as I can see, the answer is given on the Constitution Daily Blog for 9 September 2022:
On September 9, 1776, the Second Continental Congress adopted a new name for what had been called the "United Colonies".
Trying to summarise (in case of link rot), the sequence of events is something like:
- In June 1776, Thomas Jefferson's draft of the Declaration of Independence started with the following sentence: “A Declaration of the Representatives of the UNITED STATES OF AMERICA, in General Congress assembled.” This apparently makes him first to come up with the USA name.
- However, the final version of the Declaration starts with the date July 4, 1776 and the following statement: “The unanimous Declaration of the thirteen united States of America.” Notice the capitalisation. "Thirteen united States" is a description, not a name.
- The final paragraph includes the text (again note capitalisation) "these United Colonies are, and of Right ought to be Free and Independent States" - this makes "United Colonies" the name and lines up with previous use of the name "United Colonies".
- In case you think the capitalisation argument is irrelevant pedantry, it appears that Congress agrees with me because on 9 September 1776, Congrees passed various resolutions, the fifth of which reads:
“That in all continental commissions, and other instruments, where, heretofore, the words ‘United Colonies’ have been used, the stile be altered for the future to the “United States.”
Having said all that, apparently the words "United States of America" appeared in the first draft of the Articles of Confederation on July 8, 1776, as it was submitted to Congress. But the Articles weren’t ratified by the states until March 1781.