Final answer:
The details given from various countries illustrate that doughnuts are enjoyed globally in different forms, leading to the main idea that doughnuts are not solely a treat found in the United States.
Step-by-step explanation:
The details discussed all pertain to the numerous forms of doughnuts enjoyed in different countries. Therefore, the main idea connecting all these details is that doughnuts are a global treat enjoyed in many variations around the world. The correct answer is C, which states doughnuts are not just a treat found in the United States. This ties together the examples of malasadas in Portugal, bombolonis in Italy, and Berliners in Germany as international variations of doughnuts. Each of these treats represents the adaptations and unique versions of the doughnut that can be discovered worldwide, reflecting the broader concept of global cuisine diversity.