FWIW, having a joint (and much respected) army in pre-1990 Yugoslavia did not stop the country dissolving in a pretty bad civil war (or you could say war between neighbours depending on what kind of federation/union you consider Yugoslavia to have been).

Sufficiently fueled nationalistic sentiment can break through any attempt to "hide" it. Not even financial interdependence could keep the country together (plenty of companies depended on sourcing parts in other republics).