That guarantee would only be possible in a decade,not before.
Combine the current European militaries plus the production capacity of weapon systems and you will see that Europe cant even defend itself for a longer period(a month at most).
Europe’s biggest problem is not its lack of power, but it’s lack of unity. If European countries were united in the same way US states are united in a single country, Europe would be a global power to rival the US and China.
Even now, with low military spending and limited reserves of ammunitions, Europe has the capacity to defend itself against any potential enemy, except for the US.
Russia, which is the biggest threat to European security, can’t advance in Ukraine, and in the same way, it would be unable to defeat a united European front, which would have total air domination against Russia.
The problem is there is no unified Europe, and this is where the risks come from. If Russia can pick on smaller EU nations one by one, it can win. Against the whole EU, if it were a unified force, it would stand no chance.