The USA was hardly a disaster. Mutual defense is possible without unifying everything under a single government (see NATO), the US didn't even have central banking at all until the 20th century so not sure how you concluded the lack of that was a disaster within a few years of the USA being born, and "consistent policy" is something it still doesn't have in many key areas - without the USA being a disaster.
> The EU was created because the European nations wanted to be a powerful continent-sized political entity
It was created as a trading bloc, literally the European Economic Area. That project later got hijacked by federalists who wanted to do what you say, but they never had agreement on that from the actual citizens. That's one reason the UK left.
> Arguably, the US doesn't have enough centralization and this is causing many of its internal problems now.
Arguably the US's internal problems come from too much centralization, hence why Americans famously loathe Congress but like their own Congressman/woman.
The Federalist Papers explain both what was a disaster about the confederacy and why a confederacy had no possible outcome other than to be a disaster.
A quick skim suffices to get an overview of what the authors say are unavoidable failures in confederacies. Each paper focuses on a particular topic, giving examples from governments in antiquity and contemporary governments, with some exposition about how the way they were set up led them inevitably to failure in that area.
> The EU was created because the European nations wanted to be a powerful continent-sized political entity
It was created as a trading bloc, literally the European Economic Area. That project later got hijacked by federalists who wanted to do what you say, but they never had agreement on that from the actual citizens. That's one reason the UK left.
> Arguably, the US doesn't have enough centralization and this is causing many of its internal problems now.
Arguably the US's internal problems come from too much centralization, hence why Americans famously loathe Congress but like their own Congressman/woman.