So why were terrorists in the USA with links to Chechens, Bosnians and Albanians allowed such freedom of movement and were free from scrutiny to the point where even investigations were suppressed?
Our nuclear labs were pilfered. Our secrets were stolen. The Pentagon was bugged. Laptop computers with nuclear secrets "disappeared," and no one has gone to jail. And no one appears to be interested in getting to the bottom of any of it (even after 9/11).
We would do well to consider that Al Qaeda has nuclear weapons stolen from our own nuclear labs. That is our current "worse case scenario," I think, however terrifying it may be to consider.