You could stop this one of 2 ways:
1. With the $12 you get at the beginning, buy a transport and put it in the Danish Sea and buy artillery with the remaining $4 and put it in Germany (or possibly Finland). If Russia does not put any additional infantry in Leningrad with the Allies’ $12, attack Leningrad on your first turn by transporting 2 infantry and 2 artillery and maybe 1 or 2 fighters (Russia only has 2 infantry to begin with. You should also attack from Poland to Baltic States and Finland to Vyborg. This way you not only take Leningrad but you encircle it and are prepared to counterattack if Russia takes it back. This also prevents the Allies from being able to land fighters in Russia from UK (all 3 of those spaces are exactly 4 zones from UK - everything else is out of reach).
2. Buy a transport with the initial $12 and keep $4. Buy a Battleship & Aircraft Carrier with your remaining money an place them with your 2 transports in the Baltic Sea. (You could combine this with the above strategy as well if you don’t by the artillery). Assuming that you have knocked out all of the UK’s navy surrounding the UK mainland, UK can only attack your navy with their bomber and 2 - fighters on their first turn. That would be gamble for them, considering your battleship can take 2 hits and defends at a 4, the carrier defends at a 3 and the 2 tranports can be used as fodder. Assuming your carrier survives, land 2 fighters on it next round (and add more navy if you’d like) and you have a decent-strength navy in the area for UK and US to have to unseat. Having a strong navy here also gives you the flexibility to invade UK depending on the circumstances.