What percentage of the men in the U.S. are taller than 6 feet 4 inches?
What is the distribution of heights of men in the U.S.?

There's an applet called Height Analyzer at
http://www.shortsupport.org/Research/analyzer.html. 

that uses data from a 1994 survey.

According to the Height Analyzer, the percentage of men taller 
than 6'4" is 0.5%. 

The analyzer provides a graph that "shows the distribution of men's height in 
the United States. This is most well 
known as a bell curve, because it is shaped as a bell. The medium height for 
men in the United States is 5' 8½"[2]. This means that half 
of all men are taller than this height and half are shorter[3]. As you can see 
from the bell curve, most men's 
height are near the median. As you look at heights in either direction away 
from the medium, there are smaller 
numbers of men at that height. The bell curve is also called the normal curve. 
The middle 95% (mathematically, 
plus or minus two standard deviations) is the normal range. 93.6% of men are 
between 5' 3" and 6' 2"."

The Google searches you might want to try include:
height statistics
height men OR male statistics us OR usa

Not surprisingly, the average height in the US has been moving upwards with 
time. More recent data can be found at the CDC web site which gives a chart of 
heights (and weights) for boys/men and girls/women as a function of age can be 
found at the CDC web site: www.cdc.gov/nchs/about/major/nhanes/growthcharts. 
This was last updated in November 2000. For men, see 
http://www.cdc.gov/nchs/about/major/nhanes/growthcharts/set1clinical/cj41c021.pd
f. As of the most recent update the 50th percentile occurs at 177 cm (5' 9-
1/2"). The middle 95% is now between 163 cm (5' 4") and 190 cm (6' 3").