I have a tough time with west europe. Usually though I leave it pretty lightly defended, and guard berlin instead. If I can persuade the allies to land in spain, it’s not all that bad an arrangement.
Assuming eastern europe has a pretty sizable defense, and a recent infantry build in germany, that means I’ll have a bunch of infantry in germany (say 10) and armor. That will generally be enough to not worry about an attack there. This depends on the circumstances of course and how much xports are around, how much airforce, etc. But I’m going to assume there are around 4-5 xports for UK and 4-5 for the US, with not much extra air. I would play differently otherwise, and I won’t go into the thousands of different iterations. Anyhow…
If I can deter the allies enough from a western europe landing and then into spain, that’s fine. Landing in spain to me does not represent “poised to attack all territories” anymore than the UK seas does. Actually, at that point I will bait an attack in southern europe. Next turn I’ll take it back, and your fleet will be out of position for a turn, good deal. If western europe is taken somewhat lightly, I’ll take that back too with armor and planes. If western and southern are taken, I’ll try and take what I can by splitting my planes and armor, probably sending planes to western since the armor in southern won’t be subject to return fire really, and will still be in position for karelia. Fortunately on southern I can also use eastern european infantry.
Sadly, the allies can always go hard into western europe. With two rounds worth of builds there it’s not very manageable for the germans to hit it usually. So if I wasn’t planning on this I’m screwed. However, two builds worth of units for UK and US means two builds worth of units NOT in kareliea. I am hoping japan is doing pretty well in the east, they usually are. In any event, this will be my best shot at karelia, and if the allies have a good hold in western there’s not much an other option other than hold out and wait for the japanese to come to your rescue. I do not like that option.