In which country does the single banking system mainly exist

In the United States, the banking system has traditionally consisted of a number of independent banks, which usually do not have branches, each operating independently to serve a specific geographic area. This system is known as the single-banking or unitary-banking system. The single banking system in the United States is compatible with the social environment of the 19th and early 20th centuries, when social groups were widely distributed and their respective socio-economic activities were similar, resulting in smaller geographic features.