Answer:
The following are some of the reasons to consider San Francisco and Hong Kong as part of the same region:
Geography: Located on the West Coast of the United States, San Francisco is a coastal city that leads directly to the Pacific Ocean. Meanwhile, Hong Kong is a coastal city located within the People's Republic of China, that it is also located on the coast that leads to the Pacific Ocean.
Economy: Since both cities are coastal, their economies are mainly based on trade that happens through the waters of the North Pacific Ocean.
Cultural: Although located in different continents and with different predominant cultures, the fact that both cities are connected through the same ocean and are commerce partners have created a big fluctuation of people travelling from one place to the other, making both cultures to interconnect between each other.