The USSR is not conquered on the loss of Moscow, but may be forced to offer to surrender (see below); if this one-off offer, which still leaves part of the map under Soviet control, is refused then the USSR is eliminated only on the loss of her last unit. The USA cannot be conquered but will end the war at once if all France, Britain and the USSR are conquered (a Soviet surrender does not count as a "conquest" although American chances in the absence of Britain and France, the USSR having surrendered, would be minimal).