And I go hard, my passport's like a postcard
Postcards are known to have the message “Wish you were here” printed on them. B.o.B is saying that one look at his passport will make you wish you were able to go the places he’s visited. The other possible meaning is that postcards have a lot of writing on them and the large number of country stamps he has attained through his travels makes it look like his passport is full of writing.
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