Actually, I think we actually did control our own destiny. Why? In theory, the US could rack up any goal differential it wants. Let me do this formally.
Suppose we let x=the goal differential for the Czechs over Ghana (which could be anything, since I was assuming US controlled its destiny before this match.)
Thus, at this point, the Czechs have a goal differential of 3+x.
The next game is the US vs Italy, where US racks up a goal differential of y. Let's say for argument sake y=x+7 (anything is ok as long as y>x+6). So, US goal differential is now x+7-3=x+4. Italy now has 2-x-4=-x-2 goal differential.
Now, the last two games are played simultaneously. So, if Czechs and the Italians are to go through, Italy has to get more than a total of x+7 goal differential (at least) since US controls Ghana match in this scenario. So, Italy MUST score at least x+2+x+8 =2x+10 goals MORE than the Czechs.
So, Czechs then MUST have lost by at least 2x+10 goals. Thus, the Czechs have 3+x-2x-10 = -x-7 goal differential.
As you see, there is NO way the Czechs and the Italians can go through if the US controls its matches!!
So, technically, the US was in control of its destiny before this match.