Final answer:
The diffusion of cultures across national borders can have negative effects on developing countries.
Step-by-step explanation:
The statement that the diffusion of cultures across national borders can have positive and negative effects, with the negative effects more likely to be experienced by developing countries, is true. Developing countries often face challenges when their cultures are influenced by external elements, such as the dominance of more powerful cultures or the erosion of traditional practices. This can lead to cultural assimilation or the loss of cultural identity, which can have negative impacts on social structures, customs, and traditions.