I do not subscribe to most conspiracy theories, so I will largely ignore that.
As far as "Made in America" goes, the decline in manufacturing here is a consequence of high business taxes, high wages, increasingly more educated workforce overseas and a few other factors. I do not any of them include an "invisible guiding hand".
That out of the way, it is entirely possible to build a scope here and the most recent example of it is Vortex AMG (or Elcan and Tangent Theta for Canadians). There is a price penalty to that, so it is a little harder to do with mass market product, but it is clearly doable for higher end products. Each company has to decide whether it makes business sense for them to do it.
The biggest reason you see so many optical products like riflescopes made in Japan, Phillipines and China, is that several companies there decided to become high quality OEMs quite a few years ago. In the meantime, US-based OEMs (and they exist) have primarily chosen to work in field that are a lot more high end than riflescopes.
Once there is a high quality OEM or two in Japan, it is really difficult to justify starting a new manufacturing facility here. The most common model these days is to either modify an OEM's design or to design your own and have an OEM make it.
Many manufacturers are doing a mix of a bunch of things and with mergers and acquisitions, waters get even muddier. For example, I was in Colorado a little while back and visited Burris for a brief factory tour. They build quite a bit of stuff here, but none of the Burris-labeled products for the US. The assemble the T-series Steiners there and a few other hunting style scopes for Europe. They do a good job and I liked what I saw and how they do stuff, but for the prices they can command in the US market with a Burris name, an OEM makes more sense. They do check every XTR II they get from their OEM, however, which I like quite a bit. With the quality of current OEMs, you can usually count on good product, but doing QC on your own is still a good thing.
Vortex is doing something a little different with some of their OEMs where they get assembled products (it is often cheaper to import an assembled product than individual parts), take them apart and effectively re-align them at their US facility. That is partly for better QC, but partly in order to avoid disclosing some of their proprietary know-how to the OEMs.
Every company is scrambling to do things in a way that allows the to have reasonable control over the product without sacrificing profits. If they could simply charge a little more for fully "Made in US" products, they would. However, vast majority of people who say that they will pay extra for something that is made here are lying to themselves. That is why you can only do that with niche products.
Lastly, plenty of high quality optical glass is made in the US by Corning and Schott among others.
ILya