Lexicus
Deity
Only assuming that by average he meant median. If we make that assumption the statement doesn't even have anything to do with intelligence. Half of all Americans are smaller than the median American body height. Half of all Americans are poorer than the median American wealth.
IQ has the additional property that it is (intended to) create a normally distributed value over its sample set (e.g. all Americans), as Tim mentioned. In that case the median is also the mean (i.e. IQ = 100). But Gori never mentioned IQ, so I don't think the (legitimate) criticisms of IQ as a metric of intelligence apply, not to mention that they are beside the point in the first place.
I know all this, my point is that height and wealth are (relatively easily) reducible to single numbers but I don't think intelligence is (said nothing at all about IQ and Gori's comment didn't mention it either). Gori's comment only works if you reduce intelligence to a number and give every American a value.
(and yes, I know it was a joke)