Probably not directly invading, but there was a strong possibility of Germany supporting the Russian invasion, just as they're doing with the invasion of Iran.
The former Warsaw Pact countries are aware capitulating to Putin would mean they're next, so they're vocal against EU surrender. Further, if East Europe gets threatened, West Europe knows it'll have a mother of a refugee crisis - even if Ukraine falls they'll have one.
Anyway, that's all to say currently USA's geopolitical interest seems to be "Trump Tower Moscow", and Germany is not going to go along with that.
However we can still discuss what would have happened if they did.