Yes, it does become invalid. Ask the passport office to see if it makes the passport valid if you sign it again. Otherwise you may need to apply for a new one.
No, a passport is not required for travel within the United States.
Yes, a passport is required to leave the United States for international travel.
The United States issued my passport.
The United States issued my passport.
Yes, they definitely need a passport to legally enter the United States.
No, minors do not need a passport to travel within the United States.
Answer you need to get a passport
No ANSWER: Because both locations are in the United States, you will not be required to have a passport. Travel within the continental United States does not require passport.
No, you cannot leave the United States without a passport. A passport is required for international travel to enter and exit other countries.
No, you do not need a passport to travel from the United States to Puerto Rico as it is a U.S. territory.
If you are flying within the United States, you do not need a passport. If you are flying into the United States from another country, or out of the United States into another country, you need to present a passport at customs.
No, it is not possible to travel to the United States with an expired passport without any exceptions.