My brother is over six feet tall. We are of Dutch descent and the Dutch are frequently very tall. 
Oh I didnt know that Dutch people tend to be tall interesing
Yes, Dutch people are tall, though height can serve as indicator of health and good nutrition. 
on average how much taller are they then US males do you know
Human height
Human height or stature is the distance from the bottom of the feet to the top of the head in a human body, standing erect. It is measured using a stadiometer, usually in centimetres when using the metric system, or feet and inches when using the imperial system.
A particular genetic profile in men called Y haplotype I-M170 is correlated with height. Ecological data shows that as the frequency of this genetic profile increases in the population, the average male height in a country also increases.
to increase their number and diversify the gene pool, while preserving the health of the breed.
Description.
Description Appearance.
The Dutch Shepherd on average weigh between and the height varies between 55–63 cm (approximately 22 to 25 inches tall at the withers). Depending on the coat, the breed can be distinguished as short-haired, long-haired, or rough-haired.
Short-haired: All over the body, quite hard, close-fitting, with woolly undercoat. Ruff, breeches