How many United Kingdoms fit in Canada?

40 United Kingdoms fit in Canada.

Really
40
As Mercator draws it
72

Mercator makes it look like 72. The map inflates the ruler and the container both, and the ruler more.

Why the two differ

Mercator draws United Kingdom 2.90 times its true area and Canada 5.21 times. The count is the ratio of the two, so what moves it is not the inflation itself but the ratio between the two inflations. Whichever sits closer to a pole is blown up more.

Ruler
United Kingdom 248,884 km²
Container
Canada 9,986,087 km²

On an equal-area projection

Under Equal Earth or Gall-Peters the two figures are identical - for every pair on this site. An equal-area projection draws in proportion to true area, so the count you can see is the count there is. That is a definition, not a coincidence.

Open on Equal Earth