That's one of those core economic facts of nationhood that sadly does not get taught in schools anymore. An all inclusive Welfare state requires low immigration and a near zero population delta in order to be sustainable. The reason the US is not an all inclusive welfare state ala Europe is because it has been for most of its history the most open and welcoming immigration recipient. You can't do both. The math and money does not work out. It can be papered over for awhile with the wholesale exporting of raw resources such as oil and gas, but the math eventually catches up with you.