How vulnerable is Europe with a weakened NATO and Trump favoring Putin?

First of all, NATO is strengthening: even before the last meeting where Trump laid the law down, Nato was spending more on men and materiel. Second, Trump has been far harder on Russia than Obama ever was. Below the smiles, sanctions are much hasher than under Obama, and when did Obama expelled SIXTY Russian spies, as Trump did.

You have been reading too many MSM headlines, and too little detail if you believe either of your postulates.