I think it's been obvious for a long time that the alliance needs serious rethinking and revamping. I think to do away with it would be suicidal in the long term for Europe and would force us back into the agonizing choice we had to make at the beginning of WWII (which was eventually forced on us). And, no, I don't think Trump is the guy to renegotiate it. Can't bankrupt out of it, if we don't like the way the deal turned out...
There are all kinds countries waiting on the wings to fill the vacuum if NATO goes away (France, Russia, Germany), each country in its own way. Russia wants to carve countries off the Atlantic alliance and into a Eurasian alliance. Pragmatic eastern Europeans will stick a finger in the wind and relucantly re-orient towards Moscow to avoid getting "the Ukraine treatment."
France would love to re-assert the EU as a military alliance, one without the United States, and one in which France would carry relatively more weight. I believe that this Franco-alliance, especially if the Brits were to leave the EU & NATO, would be less pernicious than the Russian-lead one, but it would also be callously and perhaps reflexively anti-American.
A Germany-led alliance would be dangerous. Germany already dominates Europe economically. Add military dominance and the studious labor at excising fascism from the German psyche might prove to be shallow, and the dormant National Socialist in the German soul might re-emerge, probably without the death camps, but remaining hyperaggressive in its acquisitiveness.
Many in Europe will be quite interested in maintaining NATO, even though the US is routinely badmouthed. I attribute this to "Alabama thinking": people tend to be hypercritical of the top dog. In the case of Europe, however, the top dog is keeping the Russian bear at bay.
At the end of the day, the question is, does NATO further US interests. I believe it does.
