You are probably using the word "visa" incorrectly. You can't get a "visa" at an airport or border. A US visa is a sticker that takes up a full page of your passport and says "VISA" on it. As a Canadian citizen you don't need a visa to seek entry in most nonimmigrant statuses, so you have never gotten a "TN visa". You were admitted directly into TN status at a port of entry. If your husband is a Canadian citizen, he can also leave and re-enter the US at any port of entry (whether at the Canadian border or Mexican border or a preclearance airport), with a copy of your TN I-94 an marriage certificate, to be admitted into TD status with an I-94 expiration matching your I-94 expiration. Or he could file I-539 for TD extension of stay from inside the US (this costs a few hundred dollars). If he is not a Canadian citizen, then he will need to get an actual TD visa at a US consulate abroad, before he can seek entry at a port of entry. If his TD status (as given on his I-94) expires, and he is still in the US without a pending Extension of Stay application, he becomes deportable, and also starts accruing unlawful presence for the purposes of the unlawful presence bans.