See How Much Bigger Montana is Compared to Whole Countries
Montana is the fourth largest state in the United States, only being smaller than Alaska, Texas, and California. At around 145,000 square miles, that makes it larger than a lot of countries in the world. Europe, for example, has such small countries. So, here are all of the European countries that are smaller than the Treasure State by land size. These countries are all members of the UN, so places like Vatican City are not included.
To look up other countries and their size compared to Montana, check out the website I used here.