For the domestic airline, no that's not true, theres other airlines in the USA that have not declared bankruptcy, off the top of my head Alaska Airlines never has alongside several others. this seems to be a great, yet sadly non-exhaustive list: https://www.airlines.org/dataset/u-s-bankruptcies-and-servic...

I look at Southwest as an outlier, I don't mind them, but I don't really look for them, they used to fly to inconvinent airports.