US new fleet

I saw news today that US will have a new fleet at the southern American open sea. I am just wondering what the real purpose for all those military aircraft and watercraft for. Does it means to protect our country or it will eventually destroy civilization someday? Does the world is going to be a better if it runs by people just like me. I will not think about any reason to start a war. See how many billions dollars spend for all over the world into their missiles, weapons, militaries and defense departments. Especially in US, she is all over the world, Iraq, Afghanistan, Panama, Japan, South Korea, Israel, Vietnam...etc And all the civil war in Africa, Sri Lanka, Iceland, India, Tibet and China...etc. I still can’t imagine why they killed John Lennon. I only can imagine.