Is a seige possible in this context?
Actually, a blockade, since we only control the Indian Ocean, Persian Gulf, Iraqi, and Afghani Borders. This leaves the Turkish, Armenian, Azerbaijan, Caspian Sea and Turkmenistan borders in doubt.
Iran is 1.65 million square kilometer, and has a population of 68 million.
One of the keys is whether the US could keep the Straits of Hormuz and the Persian Gulf open to shipping of crude oil. If not, there would be a mighty conflict for the remaining supplies, with severe rationing world wide.