In Edwards' occasionalism, the created world does not contain within itself the ability to cause any effect and, indeed, does not even persist in time. Instead of God preserving creation through providence, he is actually involved in a continual work of creation at every moment. On a traditional orthodox view of second causes, we can speak of God creating a world where I drop a bowl and cause it to shatter. With Edwards, God is creating a world-moment where I drop a bowl and then (atemporally, of course, from God's perspective), creates a world-moment where the bowl shatters. There is no intrinsic connection between the two other than God's will.
On top of this is Edwards' doctrine of necessary creation and his idealism. God is bound by his own character to create and to create this particular world as the possible world most wise, good, etc. If creation, then, is a necessary manifestation of the divine character, and has its existence fundamentally in the mind of God (Edwards' idealism), and has no intrinsic ability to act, can we separate creation from God in any meaningful way? This would imply pantheism or, at least, panentheism, with Edwards' strong position on divine simplicity suggesting the former.
It should be noted that Edwards in no place admits of or defends pantheism and not everyone agrees that it is a necessary implication of his philosophy. Hodge, however, isn't the only one to have taken up this criticism and remarked upon Edwards' departure from historical orthodoxy here. Many new Calvinists take up Edwards' position on the free will in particular without having a clue that, as useful as he is, he does not represent the mainstream of Reformed, confessional thought on the matter.