One of life's little ironies is that China, who have spent decades perfecting their bureaucracy with no scrap of paper too small to stamp, actually has a more liberal visa régime than both Canada and the USA (or in many respects the UK). In many parts of China, depending on circumstances, you could have spent 3 days there without a visa (but it's rarely totally hassle free, admittedly). Each country makes their own rules. The USA enforces visas on people who stay on an aircraft which merely refuels in Guam and then takes off again.

I'm assuming you are not a USA citizen, in which case you do not need a visa.