BTUs are used a lot in Canada, but Canada only made about 9 years of progress toward metrification between 1976 and 1985, I was still in high school when our Metric Commission was abolished along with most legal requirements to use metric units, while still retaining them.

Maybe it's generational (I'm GenX), so I'm not sure if all Canadians muddle through both systems as much as I do but I seem to live in a constant superposition state between Metric and Imperial, with little sense about which I'll use for any particular purpose.

I use Celsius for cooking and low temperatures, but Fahrenheit for body temperature and most room temperatures; kilometres for long distances but inches and feet for height and most short distances; pounds for body weight, but never ounces (for that I use grams), for cooking and large weights I seem to mostly use metric units. Volumes are almost exclusively metric, I suspect because we also went through a transition when gallons shrunk from Imperial (4.54609 litres) to US gallons (3.785 litres).

I envy European consistency when it comes to metric.