Sooner.
When I served in the military Germany was still divided. At the time they were predicting that NATO forces could hold Berlin maybe three days at most, and the rest of Germany for about 10 days to two weeks.
You are forgetting that most European military forces receive minimal training, and even go home during the weekends.
Did you know that most of the American military forces "go home on weekends" (and also at the end of the duty day)?
Did you know that Danish (Infantry) forces have a basic training period that is four months (17 weeks) long?
Did you know that Finish (Infantry) forces have a training period that is between 5.5 months (24 weeks) and 11 months long?
Did you know that French (Infantry) forces have a basic training period that is three months (13 weeks) long?
Did you kn ow that German (Infantry) forces have a basic training period that is three months (13 weeks) long?
Did you know that Swedish (Infantry) forces have a basic training period that is three months (13 weeks) long?
Did you know that UK (Infantry) forces have a basic training period that is six months (26 weeks) long?
Did you know that US (Infantry) forces have a basic training period that is 10 weeks long?
Do you know which of the Danish (Infantry) forces, Finish (Infantry) forces, French (Infantry) forces, German (Infantry) forces, Swedish (Infantry) forces, UK (Infantry) forces, or US (Infantry) forces has the shortest basic training program?
They do not have a very effective military, although some of their equipment is top notch.
What is your definition of "very effective military"? Are you speaking of "military efficiency" or "military effectiveness". During WWII the German Army was much more "militarily efficient" than the Russian military. However the Russian military was much more "militarily effective" than the German military.
Even at its peak, the US had too few forces to stop the USSR, should they ever wish to commit to seizing control of Europe.
In short, the US was NOT "protecting Europe" against any real threat of invasion and conquest.
However, it did lead us to develop a military strategy and design to take out large numbers of tanks and other equipment with as little resources as possible. Thus the A-10 was born.
The US has always emphasized equipment over manpower, and the A-10 is a dead duck.
That military philosophy served us well during the 1991 Gulf War.
One of the few wars that the US has actually made a profit out of. Of course, the US was fighting against an army that was poorly motivated, poorly trained, and incredibly poorly led - so that helped.