It much depends upon couples. If a muslim marries to a Sikh, he/she needs conversions and vice versa. Much depends upon individuals, how their life is going on. "Karmi aapo apni- according to ones actions one is close or far from God" is Guru Nanak's saying. When people do not give rights to others, problems or conflicts start appearing. In India/ Pakistan/ Bangladesh sometimes these thinking cause riots, deaths etc. If one individuals joins other religion by choice, will it make any dent but it becomes talk of the house hold.
Patriotism is just an act of talking by many. When they move to other countries like US or Uk or Canada, they get their citizenship and loose Indian(Now there is dual citizenship). A few months back someone spread a rumor that Indian govt is imposing tax on NR Is on their foreign income, many were thinking to loose Indian citizenship. It is good to elevate our self first and not to interfere in others matters.
Farida Jey Too Akal Latif, Kaley Likh na Lekh||
Aapnadey Giriwan meh sir neewan kar dekh||
(If you are wise do not write bad words, look into your inside and study yourself)
Humans are effected by calonial behaviour, a Punjabi will favor Punjab and Bengali will favor Bengal.