It is not necessary for the United States to have the best army. War does not solve any problem or issue, war just makes relationships worse. As Martin Luther King said: "Violence never brings permanent peace. It solves no social problem: it merely creates new and more complicated ones.” The United States should have a strong army as any other country should, but just for protection.
The point Martin Luther King tried to make was very clear and direct. Violence only generates more violence. Using examples from reality, when the al Qaeda attacked the United States, they said that was just a response from the occupation of the US in Afghanistan. After that, the U.S immigration rules became more rigorous and the tendency is only to get worse.
As it was mentioned on the topic, evil does exist. Evil does exist and, as a country, the United States need to be prepared. The country does not need to attack anyone, it just needs to have an army to defend the territory. The army should be always prepared for something but it should never make the first move.
Mahatma Gandhi led a nonviolence resistance against British colonial rule in India. Gandhi suffered from this resistance but he kept on going without fighting back. Now he is a national hero in India. He did not use war against war and he changed the whole world with his acts.
In conclusion, the United States should not worry about having the best army in the world and the US should try to act peacefully with other countries, but always mindful that violence does exist.