Actually Americans before the 14th Amendment were actually citizens of their birth state. If you were born in Alabama then you were a citizen of Alabama and a denizen of the United States. The 14th Amendment offered Americans the chance to become US citizens in return for some meagre benefits people took on some serious liabilities e.g conscription and becoming a Surety on Federal debt.
Prior to this a citizen of Georgia could only be conscripted into the state militia and only if the state senate passed a bill. Today if the US Congress declares war then every American citizen above and below certain ages would be 'called-up'. That is why civilians were called-up for Vietnam. Your grandparents renounced their state citizenship and accepted US citizenship. However, there is a maxim in law which states: ' He who creates a liability must provide the remedy'. When you were 16 the US federal government sent to you your SS No and because you didn't realise that this was merely an offer to contract from the federal government you gave the US government joinder by not formally rescinding this offer to contract. You were perfectly free to send back that card to the government and writing upon it ' I do not wish to contract with you.' As nobody can be forced to contract against their will there would have been nothing that the federal government could have done against you, although they would have huffed-and-puffed and tried to brow-beat you. You can actually live and work in America without an SS No - although the government will never tell you this. However, you do need to know the difference between a 'contract for service' and a 'contract for hire'.
A Denizen is someone who has the right to live and work in a country, but cannot vote or hold elective office.
