You can't seriously believe Europe is defenseless without America. Germany, the UK and France are among the most powerful militaries in the world, with economies that trump Russia, and enough nuclear weapons to flatten it a hundred times over.
The countries you mentioned are as prepared for war as was France in 1939/1940
France was prepared, they just messed up the strategy. But they had the equipment, the manpower, the army was mobilized entirely after 1939, they had battle plans, etc.
Germany doesn't have a powerful military or its own nuclear weapons.
And add up all their militaries and they are still dwarfed by the US military.
The German military has issues ordering guns that shoot straight, I doubt they can project any kind of deterrence against, say, nuclear threats.