I recall a teacher in high school referring to that as “the urinal gesture.”
Body language experts (one of which I am not!) interpret this position as showing low self-esteem, weakness and passive/agressive protection (defensiveness).
But, then again, he may be placing his hand over what he perceives to be the body-part most worth protecting
Or, where his patriotism is derived from?
Or, a subtle gesture of his contempt for the USA (crotch-grab).