T,
By about UK3, the UK and USA will both have operational invasion fleets of of about 3-4 UK trns and 4 US trns.
US can then just march 8 inf to ECan for transport on US4, US5, and on and on.
After 2-3 rounds of UK and US inf reinforcement from Fin/Nor into Kar, Ger will not have enough income to produce a valid attack from EEur.
UK can also add 2-3 ftr in Kar for defence.
UK4 starts the Big Hurt by spending $3 and invading Spain. Then US reinforces w/ inf & fighters.
The combined fleet can now hit S.Eur.
A massive UK invasion can at least weaken W.Eur for the US5 follow-up.
Ger has too many places to defend at this time and would need to retreat, exposing Ukr and E.Eur to USSR invasion. Even worse, UK and USA can overwhelm the minimal defenses where Ger retreated from E.Eur. opening the Rus armor to attack S.Eur.
The point is, eventually, with $80+/round on ground and naval transport purchases, the Allies can exploit multiple attack vectors into greater Europe. ~$380+ spent by the Allies vs <$200 spent by Ger over 5 rounds. This automatically puts Ger on defense, and Ger has no mathematical way of minimizing the attack vectors short of taking Kar on Ger1, which is often a risky gamble.