[W]ithout any qualification, the word “strong” does not really mean much.

Too true. I rather wish people would simply stop using the words “strong” and “weak” with regard to patents. The words mean a million different things in a million different mouths. “Strong” and “weak” confuse more than they clarify.

I would posit that immigration is positive factor that is linked to the US having an innovative culture.

An excellent point. I am fundamentally in agreement with the proposition that the U.S. patent system is a net good for society, but so many of the arguments for the U.S. patent system make no logical sense. Foreigners are just as able as U.S. citizens to obtain U.S. patents, and foreign patentees derive just as much benefit from their U.S. patents as do U.S. patentees. Therefore, the U.S. patent system cannot (as a matter of logic) account for the U.S. edge in innovation.

Obviously, however, the U.S. produces much more innovation than most other countries, even on a per capita basis. If one wishes to account for that superior degree of innovation, then, it logically follows that one must look to some other explanation than the U.S. patent system.

For my money, the relative ease of immigration is the single biggest reason for our innovation edge. The fact that (until quite recently) we also spent more than the rest of the world combined on public funding for science is probably also a big factor. Unfortunately, we are currently dismantling both of those understruts that support our historical competitive advantage. No wonder, then, if U.S. innovation is declining.

Deleterious changes to patent law will not help in that respect, but really they are simply beside the point to the general decline. That these legal changes happen to coincide in time with the decline is largely a coincidence, not a cause.