Demographics or what happens when the majority flips

[Nik]

There are countries with sizeable religious and/or ethnic minorities with higher than average birthrates, sometimes boosted by considerable influx of emigrants. Some don't give it a second thought, others may be wary about what would happen when they outpace the traditional majority.
In Europe there are those who predict some countries may eventually become caliphates and maybe nationalism grows inter alia on these fears. In the States there are states, where white dudes are not a majority anymore, like Cali & Tex. Don't know how Texas is doing, but in California I hear whites sometimes don't feel that comfy anymore.
Is California a good example or a bad one? Is there anything to fear? It took centuries of development to negate the supremacy of the dominating race or ethnicity, would the new majorities be as tolerant? Or will the assimilation erase ethnicity, race, religion? What do you think?

[Scout]

Human nature being what it is, I have to wonder about what would happen if the tables were turned.