Final answer:
The battles of Lexington and Concord were important as they marked the beginning of the Revolutionary War, boosted colonial morale by proving they could stand up to British forces, and demonstrated to Britain that rebellious suppression would be difficult.
Step-by-step explanation:
The battles of Lexington and Concord were pivotal to the American war effort in the Revolutionary War because they represented the first instance of armed conflict between the British troops and colonial militiamen, marking the beginning of the revolution.
The British were seeking to seize colonial weapons at Concord and to capture Patriot leaders. However, thanks to a well-organized alarm system, which included the famous ride of Paul Revere and others, the militias were forewarned and ready to confront the British forces.
The British troops were harried by colonial militia all the way back to Boston following the confrontations. The battles showed that the colonists could stand up to one of the world's dominant military powers, which had a powerful psychological impact and boosted colonial morale, while also showing the British that suppressing the colonies would not be as easy as they had anticipated.
The surprise at the level of resistance they encountered and the resulting British casualties at Lexington and Concord signaled the onset of an all-out war rather than the quick suppression of a rebellion that had been expected.