A belief held by the majority does not make it better simply for that fact. Not that long ago, the majority view was that slavery was a great thing, so I think you should see that argument falls fairly flat.
Offering birthright citizenship makes the US better than 95% of the other countries. Not worse.
> Not that long ago, the majority view was that slavery was a great thing
A bit of a tangent, but is that actually the case? The highest estimate I have seen puts slave ownership at 5% of the population while the lowest puts it at 1%.
Obviously just because somebody doesn't own slaves doesn't mean they didn't support the system. There could be economic or legal reasons they couldn't own a slave.
I am just not sure that it was actually a majority view at any point in time in the US.