So if they had what you call "birthright citizenship" would they be more content with living with poverty, unemployment, bad housing and discrimination?

The problems are not caused by their status on paper, though it's probably very comfortable to assign blame to something as abstract as that. Just ask yourselves how changing the paperwork would create jobs for people who are imported with skillsets that ensure they will be unemployed because there are no jobs. And how such a change in the paperwork would prevent resentment when immigrants create ghettoes around the indigent peoples.

There have been some very succesful immigration programmes and certainly the UK, US and Autralia can obviously be seen to have benefitted widely. But that doesn't mean that a policy of indiscriminate immigration can be followed without some kind of reaction. And that reaction is there to be seen wherever that kind of non-policy is pursued.