Final answer:
The United States is the most individualistic country, with a cultural focus on personal freedom and independence.
Step-by-step explanation:
Among the options provided – U.S., Brazil, Russia, and Japan – the United States is considered the most individualistic country. This is highlighted by the country's emphasis on personal freedom, independence, and individual responsibility, which are core aspects of an individualistic society. According to sociological research and historical perspectives, the United States has a longstanding culture of prioritizing individual rights and achievements, which can be traced back to the pioneering spirit of the American West and the country's foundation on liberal ideologies that favor little interference from the state in personal affairs.