Name a country where at least 50% of people speak English
Papua New Guinea
English is the language of business and government in Papua New Guinea, which has about 850 indigenous languages.
Source:en.wikipedia.org
Antigua and Barbuda
Berlitz lists "Antigua and Barbuda" among English-speaking countries, giving an 80% English-speaking population, satisfying the prompt's 50% threshold.
Source:berlitz.com
Bhutan