Entering US with nuclear bomb is no problem

The reality is that the United States is a rather large landmass surrounded by a multiplicity of potential entry points and methods. It is impossible to stop terrorists from importing dangerous materials and/or personnel into the country entirely, and all it ever takes is one small team to cause untold havoc. This demonstrates that the need for a more comprehensiove approach to security, namely co-ordination with allies (as opposed to attempts of dominating allies), effective tartgeting of terrorists through more than just military means, and the creation of a stable global environment are going to be what stops terrorists.

:sigh: so what, after Iran's done making a nuclear weapon in a couple of years or so, there's coincidentally going to be a nuclear explosion in the U.S.?

I didn't say that at all, I was tryign to convey that simply focusing on physical border security is bad if you're trying to imporve border security.

Question: what stops people from bringing stuff across the border through the proverbial back country? Both terrestrial border are rather long, now that you think about it...

I don't think coordinating with allies is going to solve the problem as much as some would think. From what I hear, there hasn't been a breakdown in border cooperation with the Canadian government, and the border problem with Mexico is being addressed in Congress. Even then, the fact that a team of white, highly trained security agents managed to bring radioactive materials into the country isn't that big of deal, but if the radioactive sensors aren't working, then we have a problem with our technology and should correct that, rather than jump to the conclusion that we're all on the cusp of certain death.