The motives for the Second Continental Congress to break ties with England are outlined succinctly in the Declaration of Independence. The insistence of King George to heavily tax the colonies without legislative representation was the most important factor. Britain had been distracted by a European war called the Seven Year's War and was very lax in enforcing tax collection. During this time, England had basically left the colonists to govern themselves. Due to the cost of the war, England began to see the colonies as an opportunity to recoup some of their expenses. In this vein, they began to oversee the affairs of the colonies more closely. This did not sit well with colonial leaders who had grown accustomed to a certain degree of autonomy.
The colonists were also unhappy about the quartering of soldiers being required by the king. Many towns in the United States felt like police states. This often caused skirmishes between colonists and British soldiers. These skirmishes led to ill will towards England. The fact that this issue was important to the Second Continental Congress is made clear in the fact that it was written into the Bill of Rights.
The Declaration of Independence also mentions how the British do not permit the colonists to govern themselves without interference. The elite members of colonial society wanted the opportunity to govern themselves and make a profit for themselves. This was not at all possible with England ruling the colonies with an iron fist.