His concerns were mostly unfounded, since if anything the south German Catholics were even stronger supporters of unification and nationhood than their northern countrymen.
In contrast, modern multiculturalism is creating situations where you have entire sections of the population, both in European countries and the US, whose principal identity and loyalty is with other countries, cultures and religions.
Where did you get that southern Germans were bigger supporters of unification? The Bavarians liked the federation that ws the Holy Roman (german) empire — and they like the Federal republic of Germany today which gives a lot of power to the states. The southern germans did not want unification under the Prussians — the Prussian warlike and anti-Catholic culture is what defines the current German stereotype