9/11 a terror attack????

I saw a video in youtube which suggested that 9/11 attack was did by America and not by any terrorist. I was completely shocked by this video. I went further and dug out many other videos. In a video, it is clearly visible that a bomb explodes inside the building. From the day the attack was done, I was wondering how an entire steel structure can fall because a plane which hit its top part. In the tower one, the plane hit only the top part of the building. But in second tower, the plane was hit in the middle portion. I accept the fall of second tower, but I never accept the fall of first tower and I clearly saw the explosions in that video. Only George Bush has to answer these weird questions.