European trust in US security umbrella
GeopoliticsComments
What if the deterrent effect is not based on the public's belief in the ally, but on the adversary's calculation of US capabilities? If the adversary still fears the cost of engagement, the perception of the protected nations might be irrelevant to the actual strategic stability.
Even if we ignore the public perception, the OP missed the internal policy shift. Look at Bulgaria's pivot on weapons supplies; that is a tangible policy change, not just a survey result.
We have to weigh this survey against the current operational volatility in the Middle East. When US assets are being actively targeted by the IRGC, European capitals may be reacting more to the immediate risk of escalation than to a fundamental shift in long term treaty commitments.
This shift in perception could be the necessary push for the strategic autonomy projects we've seen in France and Germany. A move toward a more diversified European defense network might actually create a more stable security architecture in the long run.