For Sen. John McCain (R-AZ), the end of one of the most costly wars in U.S. history is not a reason to celebrate.

As the final American troops were pulling out of Iraq Thursday, the failed Republican presidential candidate insisted that "everything that we gained" in the war could be lost.

"It was a noble cause," McCain told NBC's Matt Lauer. "I really think we risk losing -- great risk -- losing everything that we gained, and that is the opinion of every military leader that I've talked to."

"So was this purely in your opinion, an idea of meeting a campaign promise?" Lauer asked.

"The president made a campaign promise that he would bring all the troops out," McCain explained. "It's very obvious -- I know for a fact because I was involved that there was very little real discussion with the Iraqis about a residual force being left behind, and it is what it is. And so we risk losing everything that we gained."

"As I say, we risk losing everything that we gained," the Arizona senator repeated for third time. "I think it's a great risk. And I think it was unnecessary. We always envisioned some residual force, and this administration, they were never really serious at all."

While McCain may be right that the U.S. is losing part of its footprint in the Middle East, there are some things that Americans accumulated during the war that they wish they could lose: like over $800 billion in debt and 4,484 dead American troops.

Watch this video from NBC's The Today Show, broadcast Dec. 15, 2011.