He is citizen.

[Alex snapper]

Is the sentence "He can enter the United States any time. He is citizen" correct? If so, does the omission of the the article "a" imply something special?

 

[Amigos4]

No.

The omission of the article "a" means your sentence is incorrect. The article "a" must be present.

 

[emsr2d2]

Is Are the sentences "He can enter the United States any time. He is citizen" correct?

The first is grammatically correct. The second is not. You need "a citizen".

If so, does the omission of the the article "a" imply something special?

No. The omission is wrong.

Did you write those sentences yourself?