回複：With or without New Visa Stamp

If you cross the border by land, you will be stopped by a border police. If you have all the necessary documents to enter US and don't need a new I-94, you will enter the border without leaving the car and the border police won't stamp your passport ( I believe he/she doesn't have the authority).
If you need a new I-94, you will leave your car to enter the immigration/customs room. Your passport and new I-94 are stamped there.
95% of the people cross the border by car don't have to leave their vehicles and get their passports stamped.