Towards the end of the McCullough book now – it seems that the distinctive and momentous achievement of John Adams really was making peace with France while President.
Disregarding constant warfare and ships sunk by the French, as well as world stage humiliation of American Envoys in Paris by Talleyrand and the Directorate – Adams kept cool – resisted warmongers and hawks at home – and requested peace while building a strong navy.
In the end Paris stepped down and offered peace, in 1800.
A few years later Emperor Napoleon dismissed the whole squabble as a “family feud”, and offered the massive territory of Lousiana to President Thomas Jefferson – thereby famously doubling US with a pen stroke.
Adams had declared war on France in 1798-99, US might not even have existed today.
It would probably have been crushed, opening for an establishment of a French Empire in the north-east, and very likely a lasting chaos and warfare between Britain, France and Spain on the whole continent.
If there ever was a point were the fragile young US could’ve become history, it was during those years.
And to some dismay for Adams – the news of the French Peace Treaty was delayed some months due to postal delivery – possibly costing him the general election in 1800.