I doubt Germany, to unreliable and the US has so far as I understand it only allowed Egypt to "Assemble" M1A1 tanks, basically knock down kits made in the US. I don't see the US Congress letting some foreigners build them outright.
Poland and South Korea are already working out the details to build the K2 there and that's makes more sense to take advantage of that facility than to attempt to build a plant that is likley to be targeted and there is no current supporting infrastructure. It will be 2 years at least before they can even think about planning a site and likley another 5 years before they could break ground and another two years to start production, if everything goes well. Meanwhile:
K2 Main Battle Tanks to be Manufactured in Poland for Export [INTERVIEW]