As you can see by looking at the above image (plus you know how to read odds; the lower the number, the better the odds are of that event of occurring) the US was expected get 6 points in the 2010 group stage (good enough for second place) and then win their Round of 16 match against Ghana. However, what actually happened was the US won the group (on goal differential against England) with a mere 4 points and were eliminated in extra time by Ghana.
On the other hand, the 2014 Von Trapps overachieved greatly. The oddsmakers expected them to leave Brazil without a single point. Jurgen and the boys were able to pull of the upset against Ghana and were a mere sixty seconds of doing the same to Portugal. All said, the US took second place in the group with 4 points (plus beating Portugal on goal differential). Even in the Round of 16 with their extra time loss to Belgium the US overachieved by pushing the game into extra time.
This concludes that despite the US leaving as early in 2014 as they did in 2010, they had a much better showing in 2014 due to their tougher schedule.