The Centers for Disease Control and Prevention (CDC) has suspended travel into the US from Canada and Mexico through US ports of entry by land or at entry points where US Customs Enforcement will inspect travelers at or near the borders. The reason is to avoid large groups of people congregating at these entry points with the danger of spreading further the coronavirus.
This order however, does not apply to US Citizens and their immediate family, Lawful permanents and their immediate families, US armed forces members and their immediate families, people with valid US travel documents, and foreign nationals traveling under the Visa Waiver Program, unless otherwise illegible to enter the US. Custom Officers also have the discretion to admit other travelers on humanitarian or other public health interest grounds.