In the United States, people usually address others by first name fairly quickly, especially in casual, service, or workplace settings, while using
Mr.,
Ms.,
Dr., or a professional title is more formal and often reserved for introductions, written correspondence, or when someone specifically asks for it. In schools, hospitals, and some workplaces, titles can still signal respect or hierarchy, but many Americans prefer a friendly, direct style and may invite you to drop the title after the first exchange.