Why is the US Mission called Beijing Sankuai?

Because the parent company of Meituan is called Beijing Sankuai Technology Network Co., Ltd. ..

According to Aiwen Knowledge Network, Meituan 10.3.40 1, also known as Beijing Sankuai, is not named because of the speed of Meituan, but because the full name of Meituan's company is Beijing Sankuai Online Technology Co., Ltd.