Anything is collectible. If you want a collection that will appreciate in value, that's where a crystal ball might come in handy.
As for USA made knives, there are a few good and reasonably priced ones available. Some Bucks, Case, Kershaws, Spydercos, Queen make the list. And among those, not all are made in USA. Buck, Kershaw and Spyderco make significant numbers outside the US. If it matters, Kershaw is owned by a Japanese company. I also like Leatherman knives, though the company makes no bones about using foreign made parts if necessary.
As for collectibility, Case seems to cater specifically to the collector market. The other companies have varying collector bases. Leatherman seems least collector oriented, which probably makes sense. I figure they view themselves as more of a tool company.