What Vonnegut actually does in this novel is to profoundly challenge the ideas that Americans had about themselves and about how they compare to other nations, particularly in relation to the war. This becomes painfully apparent when the American soldiers are compared to the British soldiers they are interned with, and the British soldiers are described to be physically fit and athletic, whilst their American counterparts are weak specimens who get explosive diarrhoeah on their first night. Note how this theme of masculinity is introduced when Billy has a medical in Chapter 4:
A German measured Billy's upper right arm with his thumb and forefinger, asked a companion what sort of an army would send a weakling like that to the front. They looked at other American bodies now, pointed out a lot more that were nearly as bad as Billy's.
What Vonnegut does in this novel then is to highlight that American soldiers, especially whilst under the stress and strain of fighting in a war, are completely unsuited for battle and not the Adonis-like supermen figures that they perhaps were fought to be. There is an irony when these soldiers are compared with their British counterparts: the men who are more physically able to fight in war are kept in relative conditions of luxury, whilst the Americans, who are definitely not suited to fight in war, are the ones who have to face the full horror of armed combat. This novel represents a new view of American identity by challenging the preconceptions and stereotypes of American soldiers and what it means to be an American male.