Did you know that we're only a few bridges and/or tunnels away from being able to drive or take a train anywhere in the world except for a few minor islands? (Which people typically take planes or boats to or from anyway and have no reason to do otherwise?)
Sure, some places seem so distant and impractical to travel to, and this worldwide road and/or train track would be rather...indirect...for some pairs of starting points and destinations. (Florida to London in this would involve going to long way around the world.)
Much of this is also marred by political constraints. The most logical connection from mainland Asia to Japan would be from southeastern Korea, Busan, to Tsushima, which has a ferry to the big Japanese island, and which a bridge could easily be built to. This connection would be sabotaged by the bad relation between the two countries, with Korea furious at Japan for various historical slights and modern indignities, and Japan rolling its collective eyes so often back at Korea that said eyes will fall from their collective heads if they do it any more. By political relationship, Japan would have to be connected to Taipei through Naha. This would be at least ten times more expensive to build.
Within the US, there's no good way to reach Hawaii. (Any tunnel between mainland North America and Hawaii would involve thousands of miles undersea.) And Alaska can be reached either by sea or through Canada. Hawaii should still be connected between its own islands. (Hawaii is about six islands. Ferries run between them when practical.) If Canada complained about US traffic between Washington state and Alaska going through its boarders, then the US would have to dig an expensive sea tunnel between the two. Urgh.
Australia and new Zealand would be a major pain to connect, and there's no other good connection for New Zealand. (Except maybe Antarctica, and that would be an even bigger pain to work with.) Australia would reach Asia through Papua New Guinea or Indonesia.
Probably the most profitable first connection to make would be the tip of Alaska with the tip of Siberia. (Chukchi.) If this connection were made, it would be possible to drive from southern Chile/Argentina, all the way to the northern UK, in a massive, world-spanning trip.
I tend to believe more in the obvious concrete benefits of building some of these bridges, such as increased commerce and reduced transportation costs, over the tauted benefits of increased world peace.