Yesterday the CDC advised Americans not to travel to Canada because of our soaring COVID cases.
The CDC regulates cruise ships, telling them to reduce passengers. They have enforced cleaning protocols and have strict guidelines to manage crowds and seating in show rooms. All passengers must wear a mask when they are out of their cabin except at meals where they are socially distanced. That is good advice, but most cruise passengers travel by plane to the port. They sit side by side in an airplane to get to the cruise port. The pictures I've seen taken at US airports show no social distancing whatsoever.