According to Paine, there were a number of reasons why the American colonies needed to become independent. He argued that the colonies did not need English rule and that English rule had in fact become detrimental to them.
Paine argued that Britain had only ruled the colonies for its own good and not for their good. For this reason, its rule was not beneficial. In addition, being connected to Britain had the potential to hurt the colonies. On their own, they could trade with any country in Europe. Connected to Britain, they became enemies of Britain's enemies and could not trade with them. Paine also says that Britain's system of government (a monarchy) was not at all optimal and that the colonies should become independent so that they could start to develop their own, more ideal form of government.
For these reasons, Paine argued that it was necessary and appropriate for the colonies to break away from England.