Why did Congress feel the need to boost American morale by releasing this address in early 1778?

Congress hoped people would donate much needed supplies
Americans were beginning to lose hope of winning their independence
American army had given up and began to side with the British
Congress used the address as a way to trick the British

The most likely reason is that Americans were beginning to lose hope of winning their independence. By early 1778, the American Revolution had been ongoing for several years, and the colonies were faced with a multitude of challenges including lack of resources, military defeats, and internal divisions. Congress released this address to boost American morale and inspire the population to continue supporting the cause of independence.