I would consider the term "fail" as in how it relates the the OP's euphanism that started when the big banks were threatening to do it. It doesn't relate at all. An interesting analogy to generate some new FUD, but basically irrelevant.

The "too big to fail" concept started when certain large players in the financial industry were teetering on the brink of bankrupcy, threatening to de-stabilize the entire economy. This would have been relatively sudden occurrence with swift and far reaching implications.

Any failure (or perception thereof) of the United States generally speaking, will be a slow drawn out process of transformation that takes place over a long period of time. It's already taking place and it's been going on for about 50 years. That's what the OP is worried about: something that has already happened or is in the process of happening. She doesn't like it. Alot of people aren't happy about it, and I have a few complaints myself.

But will the U.S. fail and is it too big to do so? Naw. Just inevitable change the FUDsters can't deal with.