For teaching purposes, I didn't address social security numbers and other such tangents, as it isn't strictly necessary to help non-US folks understand how the

For teaching purposes, I didn't address social security numbers and other such tangents, as it isn't strictly necessary to help non-US folks understand how the US federation compares to the EU's for the purposes of RealID. Social security numbers are a second federation ID (but not a photo ID) that anyone who pays you money is required to ask you for. You're only required to present the 9-digit ID number, not the actual ID card, oddly enough. Temporary worker visa holders are exempt for whatever reason. Untangling the intricate web between proof of birth, proof of residency of state, proof of residency of federation, and proof of taxability in federation is beyond the scope of my time available here. Disclaimer, I am not your lawyer, please seek professional guidance when making decisions.