Could there be a NATO without the US?

In a book published last year called “If Russia Wins: A scenario,” German academic Carlo Masala presented a gloomy take on European defense and NATO in the Trump era. He speculated on how things could unfold if Vladimir Putin decided to test the alliance by rolling tanks into Narva, an Estonian town of 50,000 mostly Russian-speaking residents, close to the border with Russia. The hypothetical crisis is described as unfolding in the spring of 2028 after Ukraine is forced to concede territory when its Western support collapses.