Hi Rprocter,
Welcome to the bladeforums. Sorry for your disappointment.
While I can not speak for all USA mfrs, I can speak for Spyderco. But I would guess that my comments would be true for all.
Making a quality locking folding knife is far more difficult to do that most imagine. The skill cannot be taught in schools and there are many details that require experience, testing and focus on detail.
There are very few products made where little bits of hard steel have to fit well, resist forces and still continue to perform well. This concept becomes even more unique when one couples this with a sharp and potentially dangerous edge.
I believe that all USA mfrs do try to make good product, but we find that very small details are often critical.
The interface between a linerlock and the blade tang is still a very difficult area to "get right every time" and different companies have their own specific "tricks" to try to maintain high quality and long term performance levels. Wear is a particulalry difficult area given angles, surface changes, hardness differences and of course the sometimes rough "use" a knife must endure.
Knarfeng is accurate in his analysis of US mfr. We've not given this area enough attention in the past 25 years or so. I know that we at Spyderco work very closely with the makers we work with to constantly teach each other the "tricks" we learn. This is especially important as we get into new design concept areas (linerlocks, ball bearing locks, compression locks, etc.) But we have a factory here so we're more involved in those details.
I think in the end, you will end up with several companies that you trust more than others, and you will always keep an eye out for potentials.
Many companies (like Junglee) are not owned by "knife afi's (aficianados) and must rely on the knowledge and experience of their subcontractors. Design is also a difficult area. Just drawing a "picture of a knife" is simple, right?
The Seki makers have a 1000 years of tradition and experience and much can be learned from them.
sal