The "Extreme Engineering" shows on Discovery are pretty good. I've seen the show about the Gibraltar Strait bridge a few times, and I really think it is pie in the sky. I cannot imagine the enough commerce exists, or could potentially exist to make such a connection economically feasible. Plus the engineering challenges, which are easier to overcome than the economic challenges, of building a bridge over one of the busiest sea lanes are pretty big.
Even more pie in the sky, is the Bering Strait bridge. The cost of building the bridge, plus all the neccessary infrastructure leading up to the bridge, would cost hundreds of billions of dollars. Again, I generally believe that the engineers could do it, but it couldn't be justified to the accountants.
Plus anything that relies almost exclusively on automobile traffic is suspect. Such a project should include rail as well... which the Bering Strait proposal does, along with oil and natural gas pipelines.
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia