The USSR could not have been defeated by the USA in the 1939 time period. No matter the naval power of the US, one must remember that wars are won on land and not out at sea. So, USA would have had to get into the Soviet mainland. If this daunting task was even accomplished, you must remember the only plausible point of attack is through the 55 mile Bering Strait and that the Soviets have an automatic advantage in knowing the terrain and being naturally proficient at winter warfare (due to previous hunting and living experience). Also any of the US Air Force's capabilities would be ruined. Planes of 1939 weren't prone to flying all the way to the industrial centers near the Urals, or the heart land of Moscow and it's suburbs. Also the landing zone near the Bering strait is in a geographic location that could possible the best natural defense system possible. Tundra stretching for miles, sunlight or darkness 24/7 (depending on season), and the area is a large natural spine that reaches form the Arctic ocean to Mongolia with peaks greater than 10000 feet. The USA would have to have an unbelievably well trained and massive force to even be able survive in that harsh environment. That is without even thinking about the Millions upon Millions of men that was the Soviet Army. Also Russia is well known for having the best and fiercest partisan forces in history. Honestly there is no way possible for the US land forces to attain anything but defeat in Russia in 1939. On the other hand, the USSR could possibly attain victory. First off, find me a valid source that states that the Russian Navy circa 1939 is as terrible as everyone here makes it out to be because I see otherwise( compare the number of ships pre 1939 in
http://www.innvista.com/society/gove...i/shipruss.htm and
http://www.innvista.com/society/gove...ii/shipusa.htm ). Its not like the Soviets had rafts against nuclear submarines. After the fact that the Russian navy could hold off the American forces that would be pitted against them for a period of time long enough to establish a beachhead. One must presume the fact that the Russians would attack Alaska with forces that are naturally stationed in Siberia due to their natural disposition to the environment. Also its not like Alaska is heavily defended anyway. Once a suitable beachhead and operations bases are established the Soviets would only have to travel along the Canadian coastline down to Washington state. The Russian land forces would overwhelm any resistance and the Americans would not have any Partisan capabilities due to the fact that they have never previously been exerted.
Another thing has just sprung to mind. It takes 9 hours per ship to cross the canal, which means that the transportation of an entire fleet from the Atlantic Theater to the Pacific Theater is going to take one hell of a long time. The minimum depth of the canal is also 41 feet and that isn't a whole lot. What most have failed to realize is that the U.S. Navy is known for its power due to the production of ships after and during 1939 and not the ships that were commissioned before 1939 when this war would be taking place.