It's for the common app. This is only my first paragraph... before I finish I want to make sure this is what the readers are looking for.
Prompt: Evaluate a significant experience, achievement, risk you have taken, or ethical dilemma you have faced and its impact on you.
Ever since I was a kid I knew that someday I would have the opportunity to see what is going on outside of the bubble that I live in. I live in Brentwood, Tennessee, where most everybody's opinions are the same. The surrounding areas call us the "Brentwood Bubble" because we are like our own microcosm in the state of Tennessee. Everything and anything we need is right here. Brentwood is definitely not a melting pot; I had not been exposed to many other varying viewpoints or cultures except on the news and internet. Graduating from high school and moving on to college would hit me in the face if I did not start getting exposed to the world outside the "bubble". My life changed when I went to Mexico to build houses for people in poverty in the spring break of 2007.
I think this is a very good topic choice and your introductory paragraph lays the groundwork for a good essay. This sounds like it would be a very life-changing experience for anyone, especially someone as sheltered as it sounds like you have been, thus answering the prompt very well.