Unless you hole up in some American enclave, living abroad means interacting with the locals just to obtain the basic necessities such as food, clothing, shelter and transportation. You'll discover an alien way of life that looks for the same things you do: happiness, respect and love. This increase in understanding may allow you to act as a cultural translator between America and the foreign land. (see Reference 1 under cross-cultural skills)
Your income may not go very far in the United States, especially if it's fixed, forcing you to live near the poverty level. Compare what you pay in your city with an average monthly rent of $135 in Michoacan, Mexico. You'll find similar reductions in the price of food, clothing, utilities and transportation. It's a small wonder that retirees flock to south of the border. (Reference 2)
A facility with languages is a big asset to travel and business, especially those with international customers. You will learn a language more quickly if you have to use it in your everyday life, which can only happen if you live abroad. As a bonus, in some parts of the world, like Europe, you may end up learning many languages, since people speak several of them. (see Reference 1 under linguistic ability)
Using your standard behaviors in a different country may cause misunderstandings or be illegal because you're initially unaware of what they mean. For example, talking loudly is considered boorish in Japan, entering a mosque wearing shorts is disrespectful in Saudi Arabia and holding hands with your opposite-sex sweetheart in India is provocatively rude. You may experience social rejection and legal sanction without knowing why. (Reference 3)
Not having the familiar around you, such as French fries, running hot water or freeways, may make you homesick. Unless you happen to speak the local language fluently, you may feel isolated in your inability to communicate with people and develop elections. Even if you do not understand the language, you may be dealing with the locals in a culturally inappropriate manner, making people avoid you. (Reference 1, do a find on "Loneliness.")
