All the young Dutch cheeses, as well as white French cheeses (or from other EU countries) melt extremily well. Just the heavily riped yellow cheeses melt less well. If it's young and doesn't melt, it's probably not real cheese.

Well-tasting cheeses without sodium citrate tend to break when melted

I've never seen melted cheese break. How does that even work, it's melted so in a liquid form. Even when cooled down it should be flexible and stretchy. Even when it's overly riped cheese which eventually melted (which it should, with a lot of patience) and cooled down should be more rubber-like than break.

When you think those American cheeses are perfect for their melting properties, you clearly dont have proper cheese alternatives as all young cheeses should melt flawlessly.

But the chance you don't have good alternatives is highly likely. I've traveled the world a lot and most Dutch cheeses I ate abroad were terrible. Even the craft cheeses were much worse than the plain mediocre quality supermarket factory cheeses here in NL. Even when I went to the UK, while the British themselves can make some very nice cheeses. But the Dutch cheeses they had were basically plastic, and indeed with barely any melting properties.