Iceland
Iceland is a key strategic point in the North Atlantic. Any one who has read Clancy, Red Storm Rising will see its importance. Not only is it a break pint in the Greenland/UK Gap, he who controls Iceland controls the North Atlantic by long range bombing. Any convoy would have to cross from the East Coast to the UK and France and as we see in Red Storm Rising the carnage on Merchant Men, Escorts and Carriers is abundant. Therefore the USMC would have to make an assault to retake the island, but the SBS boys would already be there doing your groundwork for you!!