The Americans felt impelled to separate from their mother country, Britain, and eventually create a dream of their own.
All men are equal - God has given them those unalienable rights. The people are those who make decisions - there is a Government, but if it becomes destructive, it is the people who decide how to organize the country.
Jefferson talks about the downsides of being a British colony, and thus creates a chance for the Americans to create a country in which these rules needn't be followed so blindly. They are free to do what they wish, because it is their God-given right.