Even if there were explosives planted in the WTC to coincide with the plane crashes and guarantee the buildings' collapse, why would that suggest it is the US g

Even if there were explosives planted in the WTC to coincide with the plane crashes and guarantee the buildings' collapse, why would that suggest it is the US government? Couldn't that also be due to Al Queda or perhaps at a higher level the Saudi government? It's not the first time that Islamic terrorists tried blowing up the building.