Why was the Battle of Yorktown important?

Ineed on 2-4 i want y’all to reply to this question so i can turn this into my teacher tomorrow

What pact signed on 1949 reinforce that the united states would not return to an isolationist policy

4. argument take the perspective of a foreign soldier volunteering to serve in the united states in the fight against the british. write a letter to family back home explaining why you have decided to risk your life in this cause. me