The United States and Canada are both immigrant countries. Why is America so difficult?

First of all, Canada is a country with a vast territory and a sparse population, with a land area of over 9.98 million square kilometers and a population of only over 33.4 million. In recent years, the aging population in Canada is very serious, so the Canadian government welcomes immigrants very much. The United States itself has a very large population, and the number of applicants to the United States has surged year by year. Therefore, the US Immigration Bureau has very strict requirements for immigration applicants, and the number of places is relatively small, so immigration is relatively difficult.