Working in the energy trading sector, when the topic of Nordstream 2 comes up, I feel somewhat obligated to weigh in. Nordstream 2 is being constructed for the most part not for Russia to sell more gas to Europe, but to have more alternative capacity that allows export of gas without having to go through Ukraine.
The main route for Russian gas has been via Ukraine, then going through Poland or arriving on the Baumgarten hub in Austria, then further distributing towards Germany, France and the rest of Europe. As you well know, for some time Russia and Ukraine do not see eye to eye. And each year the discussions on the tariffs Ukraine wishes to put for transporting the gas is a thorn in Russia's side. So they would rather export 'direct' by going around, directly to Germany. Ukraine transports between 60 and 90 BCM per year of Russian gas. The Nordstream 1 and 2 each have a capacity of 55BCM. This means that Russia could pretty much circumvent Ukraine for the most part.
As far as buying US gas versus Russian gas. You do not need to have a doctorate, that natural gas won by fracking in the US, liquefied by cooling it to minus 160°C, transporting it across an ocean and then re-gassified to put it in the transport network, is never going to be competitive on cost basis with natural gas pumped and then with high pressure delivered through an existing gas transport network until your doorstep almost. This alone makes the "buy US gas" a bit moot in my opinion.
Now concerning NATO, I would agree that this vehicle, for the purpose of being a front against Russia, has outlived its purpose a bit. I do not longer see Russia as the main threat. I would look a bit more eastward for the real threat... I see Russia rather as a big old bear in his cave next door, best left alone and not messed with its own private affairs. Communist they are definitely no longer, rather an extreme form of predatory capitalism is now in vogue there. In fact, in my mind US+EU should rather come closer in cooperation to Russia than having a bigger wedge between them.
NATO, however as a vehicle to promote military cooperation between UK, France and Germany (who have a long history of getting into each other's hair), together with the US is not such a bad thing in my opinion. It allows every EU country to save face in front of the others and keep their military sovereign and not under a EU general speaking another language perhaps, while still cooperating. It is also a great vehicle for US-EU (+Australia/New Zealand) military cooperation in my mind. Creating an effective military alliance of primordial liberal, free-market capitalist countries. That Germany, among all the others should therefore keep their promise of investing 2% of GDP into this alliance, if that is the letter of the agreement it should be upheld.
V.