Had it been Canada and the US, I'm sure they would have done the same for each other and they're not part of any union.
I don't think we can make generalizations like this because while EU is good for some things, it has also been devastating for other things like the disparity in economies in Germany vs Spain, Italy, Greece.
I have no clue how European air defense works, but I thought US and Canada have been part of Norad since the bad old days? Thus, while they're not part of a union (as far as I can tell), they share military duties in some areas.
I might have used a poor example but I think most countries on good terms with their neighbors would help each other out in an emergency without them being part of any formal union.
Had it been Canada and the US, I'm sure they would have done the same for each other and they're not part of any union.
I don't think we can make generalizations like this because while EU is good for some things, it has also been devastating for other things like the disparity in economies in Germany vs Spain, Italy, Greece.