I'm hosting Thanksgiving in Europe. I have a very small oven and a small refrigerator. What can be cooked ahead and doesn't need refrigeration?

It sounds like people have your question covered, but here are a few more ideas:
spiced nuts, roasted veggies, poached fruit (pears, quince), latkes, gingerbread cake or flourless torte, all pies - even pumpkin (even though it's a custard pie, it's far less eggs to solid ration than a crème caramel, etc.), Spanish Tortilla. I agree that a lot depends on the temperature of your kitchen.

I don't believe in refrigerating pies once they've been baked, btw, so I'm glad you won't be tempted to put your pie in the fridge.

Roast potatoes can be pre cooked almost there, then frozen. This method works well as the insides don't overcook, similar to triple cook method. Easy to store in freezer then revive when ready.

YES on storing the pie on the counter. Where in Europe? If it's chilly in your kitchen I feel like cranberry sauce would be OK too - or if you have a deep sill you could put it in a jar outside. Wait, can you even get cranberries? You could make a salad of Brussles sprouts and just fridge it, that seems like a pretty complete menu.

Here's a good place to start! https://food52.com/blog/search?q=make+ahead+thanksgiving And yes, your pie will be totally fine on the counter for a night, since it's not a custard pie.