In threads about the EU/Brexit, I've seen repeated arguments about how the EU can't function like the United States because of how much more unified Americans are now and historically. It all quite laughably ignores how all of our stability has only come from increased federal authority whenever we've had similar crises. I guess Europeans are as ignorant of American history as we are of their's.

Not really — that's the exact crux of the argument for many British and Germans, etc: "Is the EU a full federal project, with all of the responsibilities and expectations that encompasses?". In both countries and the likes of Greece, the answer has been a resounding "NO!" which leads to the inevitable and existing impasse the continent currently faces.

America is politically able to let, for example, Detroit, die a lingering death. For obvious reasons the Greeks would rather a similar fate wasn't in store for their country.

"Damned if you do, damned if you don't" as a famous early 90s child philosopher put it.

The US was not a fully federal project at its outset either, and has had to repeatedly renegotiate the terms of its union towards increased federal authority in order to avoid collapse and takeover by outside powers:

https://en.wikipedia.org/w/index.php?title=Articles_of_Confe...

States, despite all this fanciful nostalgia, do not exist in a vacuum and their continued sovereignty today is dependent on belonging to a larger unions. It's the only way to protect themselves from the imperialism of powerful federal unions like the US, Russia, and China. If any European state thinks that it can exist independently of a federal (or worse) arrangement, it has misunderstood 20th century history.

And I would also argue the election of Trump demonstrates that you actually can't allow Detroit and similar regions to wither without significant political repercussions. The Democrats tried that and it cost them the election.