The Wallabies were held at 6-6 at the break as they struggled against the Italian's game plan.
However Robbie Deans' men were able to cut loose in the second half as Ben Alexander, Adam Ashley-Cooper, James O'Connor and Digby Ioane all scored.
But despite picking up a bonus point Horwill knows his side have to improve.
"In the first half we knew they would come out and try and scrap and kick with the wind, and we made mistakes and gave them too much ball," the Wallabies captain said.
"We didn't take our opportunities when they came.
"In the second half we turned pressure into points and when we get the ball going forward, and Will Genia and Quade Cooper can get good ball, it's deadly when that happens.
"It was good to see the backs get some space and score some tries. We are happy with the result but we can certainly improve."
Deans added: "We did well in the second half, we probably did well in the first half too, although it was not shown on the scoreboard.
"We took time to settle, Italy had the benefit of the breeze in the first half but our intensity at the contact area was better in the second half."
Deans was also full of praise of his side's scrum after it coped reasonably well with the vaunted Azzurri pack.
He said: "We are pleased with the scrum, we have worked hard there. We are happy with the progress we are making and hopefully we can continue to do so.
"It's good for the group. Getting the result was key. We have a lot of respect for the Italians, they defend well and will cause sides problems."
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