To answer your other questions, (sorry I went off recounting my youth) I believe that the hydraulic excavator blind sided the U.S. manufactuers. By the time they caught on as to how important and useful they were, the Japanese machines were in their 3rd or 4th generation and vastly superior. So, instead of starting from scratch or redesigning their offerings and play catch up, they simply imported some.
Backhoes for the most part are made here for this market at least.
To my knowledge, Cases are produced here.
Cat has factories in Virgina (I think) and Great Britian for backhoes. Could get one from either place I understand.
JD is here.
Terex machines are made by Fermac of Great Britian.
Dunno where New Holland (fiat hitachi elsewhere) makes anything.
JCBs are produced in Great Britian and I think they have a factory here too.
The why is sorta complex, Economics in college will teach you some of the whys. (if you get a teacher worth a $%@#)
Backhoes are somewhat an american machine. In japan, for example, excavators or minis do pretty well all the digging from what I've seen. Backhoes are also seen in Europe, but not to the same extent. Wheeled excavators are popular in Europe as they can be roaded, saving truck expenses. Travel distances are typically not as far in say, England as here.