Some do and some don't. English is more commonly spoken by the younger generation, as either a first or second language, but older First Nation's people may only speak their mother tongue.
For example, according to a 2006 report by Statistics Canada:
English and/or French were the primary languages spoken at home for 90% of off-reserve young First Nations children.
England was the first nation to speak English
First Nation schools are called Residential Schools, and they forced First Native students to speak English and tried to force them out of their religious beliefs.
Portugal was the first nation to speak Portuguese
Australians speak English because the first Europeans to settle the continent were the British.
About 1.5 billion people speak English as either a first language or second language.About 9.2 million people speak Swedish as either a first language or second language.So about 1.49 billion more people speak English than Swedish.
Michigan has no official language but most of the population will speak English, or American English, as their first language.
The people of the first settlements were British, so that is why we speak English today and most of the people living in Australia are Christian.
More people speak Spanish as a native tongue (first language) than English, but more people speak English as a second or third or fourth language than Spanish.
The majority of people in Spain speak Spanish as their first language, around 95-98% of the population. English is the second-most spoken language, with around 27% of the population having some level of proficiency in English.
English is not the first language of India, and it should not be, because not enough people speak it as a first language.
About 500,000,000 people speak English as a first language, so that would be around 7% of all humans speak English as a first language. As any other language but first, it is estimated that 2,100,000,000 humans speak English, or about 30%.
When the English came to Australia the people that inhabited Australia did not speak English. As a matter of fact there are still places in Australia where English is not their first language.