An equaliser in the final minute of stoppage time earned the visitors a point against the world champions in Gelsenkirchen, and O'Neill was quick to pay tribute to the resilience shown by his team in the Group D clash.
"It was a terrific effort," O'Neill told Sky Sports News. "We were backs to the wall in the first half.
"For periods in the first half, we were under pressure but we had to take that into consideration. It was a similar situation in the second half.
"When they scored, that changed out mindset and we had to go in look of the equaliser and we kept going until the very, very end. Our spirit carried us through."
Ireland have picked up seven points from their opening three qualifying games.