Montana is around the same size as Paraguay.

Paraguay is approximately 406,752 sq km, while Montana is approximately 376,979 sq km, making Montana 92.68% the size of Paraguay. Meanwhile, the population of Paraguay is ~7.4 million people (6.4 million fewer people live in Montana).
Tip: This to-scale comparison of Paraguay vs. Montana uses the Mercator projection, which distorts the size of regions near the poles.