Palin, 44, said she did not "blink" when McCain, the Republican presidential candidate, asked her to join him in the race for the White House.
"I answered him yes, because I have the confidence in that readiness and knowing that you can't blink, you have to be wired in a way of being so committed to the mission, that mission that we're on, reform of this country and victory in the war, you can't blink."
The first-term Alaska governor was a relative unknown in US national politics until McCain, 72, picked her two weeks ago to run against Democratic rivals Barack Obama and Joe Biden.
And McCain's camp had kept her shielded from news interviews - to give her time to receive foreign policy coaching, according to the AFP news agency - until the ABC appearance on Thursday.
On Iraq, Palin defended a past statement that the war there was a "task from God", saying she believed in a divine plan for the good of the world.
She also said the war was for "America's cause ... a righteous cause" on Thursday as she officiated at a deployment ceremony for her son's unit which is set to head to Iraq in the coming weeks.
Taking a hard line on the crisis in Georgia, Palin said the US would be obliged to defend it from another Russian invasion if the former Soviet state joins Nato.
"We cannot repeat the Cold War," she said, adding that Ukraine should also consider being in the Western alliance to prevent an armed conflict with Russia.
Palin also said that the US could not allow Iran to possess nuclear weapons.
"We have got to make sure these weapons of mass destruction, that nuclear weapons are not given to those hands of [Iranian President Mahmoud] Ahmadinejad, not that he would use them, but that he would allow terrorists to be able to use them.
"We have got to put the pressure on Iran," she said.