But the EU foreign minister can be contradicted by basically any country president/prime minister or their foreign ministers if it says something that is not aligned with every other EU member.
Then you are misinformed.
Because it happens continuously.
Canton executive argumenting again "conseil fédéral".
Local Syndic (Mayor) arguing against Canton decision.
Local parlement trying to address or delay legislation or arguing against Berne ones.
Just open a random news paper.
This is democracy, like it or not.
In your example, the mayor can criticize the canton decision, but he cannot do anything about it. That's the difference.