回複：由加拿大返美差點被拒入境 - 應該放你進

根據國務院的這份文件: 過期的F-1簽證可以在加墨入境時自動延期和更換類型. 你用的30天條款是I-94背後的把? 你應該打印這個文件就好了.

http://travel.state.gov/visa/laws/telegrams/telegrams_1441.html

---------摘要-------
(i) The validity of an expired nonimmigrant visa issued under INA 101(a)(15) may be considered to be automatically extended to the date of application for readmission, and

(ii) In cases where the original nonimmigrant classification of an alien has been changed by BCIS to another nonimmigrant classification, the validity of an expired or unexpired nonimmigrant visa may be considered to be automatically extended to the date of application for readmission, and the visa may be converted as necessary to that changed classification.