Kellie Pickler, on her USO tour

Kellie Pickler just returned from a whirlwind USO tour of military bases around the world, and the exhausted country singer says she can’t shake two things from her mind.

“Seeing the faces of over 20,000 military men and women (that is forever imprinted in my mind),” Pickler writes in a new post on her MySpace blog. “And … the horrific endless sight of porta potties (that too is forever imprinted in my mind).”

Seriously, though, Pickler, 22, says the response from military personnel around the world – the tour took her to Germany, Afghanistan, Iraq, Kosovo and England – deeply impressed her.

“I just got back from my second USO tour. Once again, the most incredible thing I have ever done in my life. … THANK YOU, THANK YOU, THANK YOU to the men and women serving our country,” she writes. “I will never take what you do for granted.”

“I am more tired than I have ever been in my life and I don’t mind it at all,” she also shares. “I don’t think I have ever flown this much in my life. … If I remember correctly we did 9 shows in 5 days!!!! I guess I am still on auto pilot.’

As she notes further, “I don’t think this trip has really sunk in yet so it might take me a while to absorb everything.”