Birthright citizenship in new world countries like Canada, USA, New Zealand, Australia, Brazil, Mexico, Argentina etc makes perfect sense because the vast majority of the population in these countries are descendants of immigrants. The actual indigenous natives of the American and Australian continent, (the Māori, Aboriginals, Choctaw, Cherokee, Shawnee, Seminole, etc) were exterminated and subjugated through warfare, massive, continuous and relentless European immigration/settlement, territorial dispossession, diseases brought by colonizers and genocide. As a result, the descendants of the remaining native survivors live in “Indian reservations” exclusively designed for their own people. The only obvious exceptions to the rule are the ancestors of modern Black Americans and Black Brazilians who were imported by European slavers without their consent to these countries because of chattel slavery.
Right of Blood citizenship only makes sense in India, and in European, African and Asian countries. The old world. Why ?
Because the natives are the vast majority of the people in most of these countries. The purpose of Blood citizenship laws is to protect the sovereignty of a nation and maintain the ethnic and cultural integrity of the native citizens whose ancestors lived on their lands for millennia . The purpose of Blood citizenship is to claim ancestral rights and preserve the demographics of the native population. The old world functions on Ethnic and tribal nationalism, bound by kinship ties and blood, New world operates on civic nationalism, bound by ideas and common culture.
For example, the ancestors of the modern Italians were living in Italy 500-1000-2000 years ago. Same situation in China, Japan, Senegal, Ethiopia, Iran, Tunisia etc. The ancestors of the current American citizens lived in Africa, Europe, Middle East, Asia, Aztec Empire 500-1000-2000 years ago. Most Americans don’t descend from the real natives of this land.