You MUST have US Citizenship in order to apply to a US Legacy or Cargo Carrier. The Regionals will take you with permanent residency (green card). US Citizenship can take 10 years to obtain. So, that's you flying for a regional for 10+ years.
Ah, negative ghost rider. Not only untrue but illegal under US law. Worked at 2 Regionals and now at UAL, without US citizenship and just a Green Card.