What good will that do? The constitution only states that the president himself/herself must be born on U.S. soil, but not a single letter is there about their spouses.
Of course we already know that Melania is an immigrant since she was born in Yugoslavia (back then that was a country. The area she came from is now Slovenia, but back then it was Yugoslavia), so we already knew even before Trump became presidents that he has a bit of double standards when it comes to the immigration topic, and funny enough, he's not the only anti-immigrant populist in the world with double standards like that. Despite all that, Trump still gets all the support by anti-immigrant supporters, and you can't tell me they didn't know that :P