Final answer:
Paul Rand was an influential book cover designer in the United States, known for his iconic logos and lasting impact on graphic design.
Step-by-step explanation:
The most influential contemporary book cover designer in the United States is a subject that could be debated, as design is subjective and there have been many talented individuals in the field. However, it is widely recognized that Paul Rand was one of the most successful and influential designers in America, especially noted for his work in the 1950s and 60s. Rand was known for creating some of the most iconic logos and cover designs, with several companies still using versions of his original designs today. This longevity and continued relevance in corporate branding and design underscore Rand's profound influence on contemporary graphic design, including book cover design.