English became widespread globally through the expansion of the British Empire, making it the clearest answer to this question. British colonization, trade networks, administration, education, missionary work, and migration carried the language across North America, the Caribbean, Africa, Asia, and the Pacific.
English spread in different ways in different places. In settler colonies such as Canada, Australia, and New Zealand, large-scale migration established English-speaking societies. In many parts of Africa and Asia, English became an administrative or educational language alongside local languages, often remaining important after independence.
The language later gained further international influence through the economic and cultural power of the United States, itself a former British colony. Modern English includes many regional varieties, such as Indian English, Nigerian English, Singapore English, and Australian English.
Portuguese, French, and Spanish also became global languages through their own empires. English is the canonical answer here because British imperial expansion was a major historical force behind its worldwide distribution.