Muse,
This is how I see the problem:
The need to create an economic zone, that shall force us (all the parties) into mutual and sustainable growth, is urgent. It is urgent because the central country, Afghanistan, is not independent in true sense. It cannot decide on its own and keep undesirable intruders out, simply because it is not a functioning nation. Because of this condition of Afghanistan, it remains very vulnerable to any sort of take over, for example the Taliban in earlier times, the US now, and who knows who comes later. The economic zone involving all the parties will have to be created much sooner to avoid any such take overs in the future, because once a take over is done, and any single country gets hold of Afghanistan, the olive carrying dove will be shot down in a minute.
Having said that, I feel the need to clear a couple of points for all the members here.
1. The impasse we are experiencing in the relationship between all the countries in the region can be simply attributed to the lack of consensus among all the countries. There is no way to reach such a consensus, unless forced upon by another party that all the countries in the region depend on.
In this case, the US can play a part to force such a consensus, and of course the degree of involvement of the US in the region will be defined by the countries in the region. We can be very sure of a lower degree of US participation in such mutually beneficial trade because no country in the region is a big fan of the US. And India certainly is among the very wary ones when it comes to US 'hegemony'.
At the same time, the US too would want something out of such a scenario for itself. It can be more than satisfied by feeding the oil through Arabian Ocean, but only under the secured supervision of Indian Navy, and no presence of any American boats (military/navy ones).
The land trade, and the trade route will depend a lot on the purchasing capacity of the nations involved. While Pakistan does have a strong market, I am skeptical of the Central Asian Nations (except, of course, their being the source of energy). May be with time such a route can be further extended to Europe. But that's just a bit too far fetched an idea for now.
2. If the US were to be thrown out of the region, then the impasse will continue. Truth is, India shares no border with Afghanistan, yet strongly desires its presence and influence in that country. With Afghanistan in its backyard, Pakistan - an enemy nation of India, will never allow India's presence (for valid or invalid reasons, that is a different question).
With the ever changing sociopolitical environment in Pakistan, where people are used as more of an instrument by the ruling parties, we can never be sure of what may become of Afghanistan. Secondly, even if some sort of India's civilian presence in Afghanistan is tolerated by Pakistan, it will still make the trade route to CANs much more taxing than desirable (for some strong reasons that can be discussed later). However, Pakistan all by itself will not have a lot to offer the CANs if any sort of trade route were created and practiced upon.
Now coming down to the major reason why it will not be easy to formulate the US's role in the region. The US would indeed want to create problems in Iran. Even bigger ones, if the US gets to create strong bases in Afghanistan. That will not be acceptable for the reason that Iran too may want to play its part in the route and trade that follows. However, judging by the recent behavior of Iran, it will be extremely difficult to keep even the minimal presence of the US in the region, and when it happens with Pakistan's nod, there will be even newer problems.
In conclusion, I see the presence of the US (which will have to be offered something of great value, since its economic conditions in present times may not allow for a longer presence) undermined by only one country - Iran. At the same time, we should also keep in mind that Iran can easily use the Caspian to have its own trade route bypassing Afghanistan completely. Besides, Iran does not have much to offer to the CANs than it does for other far away oil starved nations.
Thus, if we all were to create an economical balance amongst us, all the while when we cannot look away from our differences, then we will need the presence of a powerful middleman that happens to be Uncle Sam at the moment - Simply because we are already deep in "mutual blackmail" with that middleman.
Without any such powerful middleman, India cannot even step inside Afghanistan to offset the presence of Pakistan, and it will be a repetition of '94-2001 Afghanistan.
