If you are a foreigner then Yes, it is safer and best to travel with your passport. You may also need a Visa if you are not a citizen or depending on where you are from.
If you are a foreigner yes you need a passport as well as a travel visa to enter the country unless you are part of the ASEAN where you only need you passport.
No.
You need a passport if you're a foreigner. If you're a US citizen, you need your US driving licence.
Alaska and Hawaii (which are U.S. states) and the Virgin Islands (which is a U.S. territory) do not require a passport if traveling within the U.S.
Alaska is one of the 50 states of the United States of America. If you are a U.S. citizen you would not need a passport as you are traveling within the country... not to Canada.
As both Maine and Alaska are U.S. States, you do not need a passport to get there.
You need a passport
I would think not on the passport. All airports (to my knowledge) require an ID. Since you're going from one US state to another, I don't see the need for a passport. I'd call your airline or travel agent just to be sure.
Yes. Every foreigner entering the United States must have a passport.
No, passport requirements are not for domestic travels. Though passports can be used as a picture ID for boarding the plane.
No, you do not need a passport inside the US but you will need a valid picture ID.