Technically, residents of Puerto Rico are not citizens so long as they reside in Puerto Rico. They are US subjects, living in a US territory, with only part of the rights of a full citizen.
But upon entering any of the United States that have been admitted to the Union, they assume the mantle of citizenship, and once residency is established, have all of the rights of any other US citizen.
People from Jamaica or Bermuda or Haiti do not have that same privilege.
Nope, sorry...Puerto Ricans have been FULL citizens since 1917...
Talk about angels dancing on the head of a pin. A distinction without a difference.