Many countries use English, probably more than we can think of. There are several good reasons for this point. First, part of the reason English is a global language is because of colonialism. The British Empire at it height was really spread out over the world. For this reason, they brought their culture as well as language. Second, with the rise of America as the economic powerhouse of the world in the last century, people wanted to learn English to compete in the American market. These two reasons are probably the most significant in explaining why English is spoken in various countries.
Language Acquisition is a process that involves behavioral, cognitive, social, and psychological input. When the colonists arrived in Plymouth, and later developed the Jamestown colony, they brought with them their religious, social, romantic, literary, scientific, and provincial language usage.
As the groups began to separate due to religious preferences and form their own groups (as in the case of Pennsylvania), or for political reasons, the homogeneous groups began to identify themselves with their idiosyncracies, and not only began to discover new things that they would find names for, but do to the consistent interactivity and the fact that they wanted to identify themselves not as Englishmen, but as colonists, they delineated psycholgically and sociologically unique manners of communication than later continued to repeat themselves from generation to generation.
According to the ideas of sociolinguistics, each society puts its own stamp on a language. Because of this, you can say that English belongs to each country in which it is widely used.
Languages do not stay static over time and place. They change based on the needs of the individuals and groups that use them. Once the basic language is changed by the needs and usages of a group (in this case a country), it becomes almost a different language.
Thus, the English used in one country is no less valid than that of any other country, regardless of where the language originated.
English is the most widely spoken language in the world. It is the native language of more than 500 million people in countries like UK, Ireland, USA, Canada, Australia, New Zealand and South Africa. Then about 150 million people in countries like India, Pakistan, Bangladesh, Sri Lanka and many African countries speak English in addition to their native language. In addition more than 200 million people all over the world know some English.
The English language, as its name implies originated as the native language of the English People. Seventeenth century onwards the English Language spread to other parts of the world as English people explored and colonized may different regions in Africa, Asia, Australia, and Americas. Around mid nineteenth century, England had expanded its empire to the biggest empire on the earth that ever existed. This combined with development of English as the native language of USA, made this language the most useful language to learn for people interested in international business. And with this more and more people started learning and using English, and with that utility and usage of English went on increasing, till it came to be recognized as the Language for all international business including, business, scientific research and politics.