Its not that the US has abandoned NATO. Its that its NATO allies have abandoned having real militaries:

Second, and far more serious, is the awareness that the new NATO of 26 nations, will be less a military alliance than a political club, an institution that is meant to embody the diplomatic and political community of the Atlantic nations, while resting on a fragile military base. The fear is that NATO is degenerating into a talking shop, a miniature United Nations, with all the frictions and weaknesses of the United Nations, but lacking the legitimacy that comes from the presence of every nation on earth.

Also see Martin Walker's previous column on how wrong the Europeans have been in their disagreements with the US. Its also here.