In North America [The United States specifically] uses a combination of Imperial and Metric measurements . You may dislike the imperial system (and that is ok, I dont like the metric) but it is what it is and disliking a video because of this is not acting in a mature way. I, like many others, have learned to do conversions in our head. Its very simple. Centimeter to Inch is 2.54cm to 1inch.
@christian franca this chart may help you to some degree. I hope you continue to enjoy LTT material.