The bearskins referenced above, introduced IIRC by Napoleon for the Imperial Guard and since borrowed by Guards regiments of many European nations, were adopted in part precisely because they made the wearers look taller and more intimidating (also, Grenadiers traditionally were bigger than the average soldier). And guardsmen were usually recruited for height. The Prussian Guard of WWI, some of whom faced Tolkien's division on the Somme, were all 185 cm or taller.

As to Presidents: Shrub may be an exception, but the trend post-WWII has been for the taller candidate to win the election- Reagan, Bush Sr, and Clinton were all well over six feet.

Oh-as to Boney's height.

The source of the confusion lies in the fact that early reports that didn't use the metric system (official but not necessarily widespread at the time) used the old royal French foot- which was slightly longer than the English foot. English translations tended not notice this or make the conversion, giving an erroneously small figure. Boney was in fact 1.7 meters tall, or 5'6."