The fact Trump is a viable candidate under any circumstance indicates the USA is already a failed state. The only matter up for debate is how long it circles the drain.
I agree, it is a very bad sign, but the idea that we are either a "failed state" on the way to oblivion, or doing great, and there's nothing in between, is silly. We're a lot better now than we were when only landowners could vote, right? Or before the civil war and the second founding? Or before women gained suffrage? Or in the leadup to our entry in WWII, when it looked like we might just join the Axis powers? Or the nineteen forties, when "separate but equal" was basically unchallenged? Or in the nineteen fifties, when a woman was a housewife or nothing? Or the nineteen nineties, when "don't ask don't tell" was actually considered a victory for LGBTQ+ rights? Or the twenty-aughts when people were noy allowed to marry based on gender? We're trying to decide, right now, if a former president can be tried for crimes - it seems wild that this should even be a question, but when it was Nixon, Johnson pardoned him, and that was it - we might be on the verge of a huge step forward, in even just going ahead with the trial, no matter the outcome. Does all this mean everything is awesome now? Oh, oh, HELLS NO! It's a mess, but it doesn't mean we are a "failed state", it just means we aren't there yet, and we gotta keep struggling.