The 32-year-old "Cowboy Casanova" hitmaker said it was tough for her to stay away from her hometown for so long, reported Us magazine.
"Idol was probably the most horrifying thing, because I had never been away from my hometown like that before. I was in LA, of all places, by myself, putting myself out there, which is a scary thing for anybody to do. My first plane ride was when I was going out to LA alone," Underwood said.
The seven-time Grammy winner admitted that she only wanted to gain good experience through the competition.
"Because I am always a practical thinker and would never allow myself to think it would turn out okay all the time," she said.
Despite her superstardom, the mother of one still gets nervous during performances.
"I still haven't figured out how to talk to the audience. I just want to sing. I am a little awkward when it comes to speaking, because I am a shy person.