The scenario that best describes an effect of the diffusion of U.S. culture is:
"A person in Paris, France, takes their date to a fast-food restaurant for dinner."
This scenario illustrates how American fast-food culture has spread and become a part of dining choices in other countries, showcasing the influence of U.S. culture on global eating habits. The other scenarios may involve cultural exchange or influence but do not specifically reflect the diffusion of U.S. culture in the same way.