The POD is that the American colonies break from Britain as in IOTL, pretty much the same ones though there can be one or two differences, but not in the 1770s. The British government abandons any thoughts of trying to get money out of the colonies, either by internal taxation or even just actually enforcing the customs duties, and somehow manages until the French revolutionary wars/ Napoleonic wars.
Note that this could likely butterfly away the French Revolution, but at some point there is going to be another major war between Britain and France, probably another major continental war, and the foundations of late Bourbon rule in France had been pretty undermined.
The break comes between 1800 and 1830. It could be a British move against slavery, a later attempt to get revenue from the colonies to try to fight a war against France, or a revolutionary regime in England itself (something like this played a part in the Spanish and Portuguese colonies leaving). But for whatever reason, the break occurs twenty five to fifty years from when it did.
What are the leading effects on the development of the United States, if it is still called that?