Hah! I wasn't meaning the average individual intelligence, just the ratio of an individual's capacity of understanding to everything that is understood. Since that ratio is very very small, even amongst the brightest, the average person's knowledge on any random subject is going to be abysmal. Combine that with group psychology, and you see why large groups tend to make awful decisions. The few people who do know about that particular subject get drowned out by the vast seas of those who don't. That said, there is a lot that could be done to raise the average person's awareness and ability to think critically about common issues.
Eh. The U.S. has always been a country of immigrants with a regularly shifting face. This isn't the first time there has been an immigration backlash and it probably won't be the last. The same doom and gloom predictions that are circling now were circling then.I think the modern equivalent of the Visigoths are speaking Spanish these days.