The Constitution didn't endure. The Articles of Confederation failed right off the hop, and the Constitution itself failed in just a hundred years. Add in the fact that separation of powers has been an abysmal failure; that the electoral college system is f**k stupid and always has been; and that the only way for the federal government to regulate most of the modern economy was through a laughable court decision that expanded the commerce clause to be basically meaninglessness... Well, let's just say it isn't looking good. It took two SC decisions over twenty years just to make it so the government could make child labor illegal The system of government created is vastly inferior to any parliamentary system in the Western world.
Beyond that, in regards to slavery, WWI, WWII, etc. it really is impossible to say how it all would have turned out. I can think of a dozen different scenarios, as I'm sure you can. The greater point is that you probably could have achieved all the same things without murdering your countrymen. Slavery was abolished sooner and with less bloodshed literally everywhere else, and the Founding Fathers were the ones responsible for the widespread belief that treason and violent rebellion is some sort of moral democratic duty (the tree of liberty etc). It is no wonder that things got so messed up - the Founding Fathers spread a creed of violent, antisocial individuality. Even today your national mythos are a poison to the civic body.
Dumb radicals who spazzed over nothing.