I see how it may look like this from the outside. But I think it would be like saying that siblings hate each other because you witnessed an argument.
Most people in most EU countries consider the other EU countries as allies, even though they don't agree on everything. Now the fact that 27 countries argue means that they talk to each other. I think it's a lot less polarised than in the US. Or course there are extremes too.
On the positive side, this shows that the EU has gained a level of international influence that is taken very seriously by other major powers. It's not 100% certain that it will survive this current wave of assaults, but if it does, it will be even stronger.
That is also why the nationalists inside of Europe want to be friends with those other players: because if you want to make Europe weaker (because you think you are better off on your own as a European country), then your interests align with those other players.
Let's not pretend that nationalism doesn't have deep roots in Europe.
From the top of my head, Franco, Hitler and Mussolini frequently helped each other, two of them even created a somewhat famous alliance together, even though by their own "theories" they should have been fighting against each other instead.
I'm sure there are even more examples further back too.