Hello? The socialists are in charge. The trouble is, birthright citizenship conflicts with their open borders agenda and they haven’t figured out what to do about it.
I was not clear. By example, USSR never had an open borders problem. Neither does Cuba, Venezuela, North Korea, China, North Vietnam, etc.
European (soft) socialism is a different animal. Socialism there has not done enough damage such that they need to close their borders to keep people in.