Like @amacy, I did a quick search and couldn't find the text of the original speech either. But my best guess would be that it was simply a slip of the tongue. He probably started out intending to say, "More and more of our oil is imported", changed his mind to, "More and more of our oil comes from overseas", and just jumbled his words.
In fairness to Mr Bush, we all do that sort of thing all the time. You can find equally jumbled words from Mr Obama. Like I just found, "The reforms we seek would bring greater competition, choice, savings and inefficiencies to our health care system." Obviously he meant to say that his plan would reduce or eliminate inefficiencies but when he mixed that in with "greater competition", etc, it came out wrong.
I bet you make such mistakes all the time. I certainly do. The difference is that when you or I make a verbal slip, half the time no one notices or cares, and the other half of the time we just say laugh and say, "Oh, I meant ..." and no one thinks anything of it. But when it's a big-time politician, there are reporters following him around every waking moment and recording everything he says, and when he makes a slip, political opponents quote it over and over, and play the video over and over, to prove how stupid he is.
When you like a politician, it's obviously a slip of the tongue and you know what he meant. When you don't like a politician, it's proof that he's stupid. Like, Mr Bush once mispronounced "strategy" as "stategery". Mr Obama once mispronounced "corpsman" as "corpse-man". Which was an understandable slip of the tongue and which demonstrated that the speaker is an idiot? I'll bet your answer depends a lot more on which politician you agree with than on the actual words or the context.