all the other NATO troopsThe mood in the USA is turning more inward. There is less appetite for NATO. The sentiment is moving more toward: if the Germans don't want to be learning to speak Russian, then they should be paying for more of their own defense. But they're not:[1]
in terms of share of German GDP, military expenditures remain average at 1.2% and below the NATO recommendation of 2%.
I'm personally astonished at how little of an Army Germany has today. Especially considering that just a few years earlier, Eastern Germany was studying Russian in school and was a large component of the Warsaw Pact.
Poland is quite afraid of Putin. But Germany seems to have adopted a "meh" attitude toward the whole situation. They probably think that if they sell enough BMWs and Mercedes to Russia that everything will turn out OK. And probably it will.
Edit:
Germany doesn't need an invasion force, just a defense aided by dozens of other countries by treaty.
Just want to add that I think you're wrong about this. There is a world of difference between large integrated forces, such as the US V Corps and VII Corps in Germany during the Cold War, and what exists in NATO today.
Nowadays, some of those "dozens of other countries" would contribute what, perhaps a battalion or two of combat troops? Not the same as when VII Corps deployed from Germany to Iraq and defeated the Iraqis in the first Gulf War. Not the same as when V Corps deployed from Germany to Iraq and defeated the Iraqis in the second Gulf War. Both those Corps have been deactivated. Nothing took their place.
Total US force in NATO was 67,000 in 2015. Not as big as one might think.
Here's a "semi-official" NATO statement about force levels: Some 25 per cent of NATO members do not have an air force, 30 per cent have no naval force or maintain a navy with less than 600 sailors, and 50 per cent are fielding an active army of less than 20,000 soldiers. NATO is an Alliance of unequals [2]
Finally, the other side is now run by an ambitious, intelligent, charismatic leader in Vladimir Putin. It's no longer led by Boris Yeltsin the drunken bum, and hasn't been since 1999.
[1] https://en.wikipedia.org/wiki/Bundeswehr
[2] http://www.nato.int/docu/review/2015/Also-in-2015/europe-def...