No you do not.
However, those who travel by car or bus will be stopped at many Immigration checkpoints along the way and will have their citizenship challenged by DHS officials. People who "look Mexican" are given close scrutiny.
Yes, you do not need a passport to travel to Texas if you are a U.S. citizen. However, if you are traveling from another country, you will need a valid passport and possibly a visa.
No.
no
No you don't. Travel within the United States does not require a passport.
Yes, you need a passport to travel to Europe.
Yes, you need a passport to travel to Paris.
You need a passport
Yes, you need a valid passport to travel to Australia.
No, you do not need a passport to travel to Florida if you are a U.S. citizen.
Yes, you need a valid passport to travel to India.
Yes, you need a valid passport to travel to Peru.
No, you do not need a passport to travel within the country.