Maine is around the same size as Serbia.

Serbia is approximately 77,474 sq km, while Maine is approximately 79,931 sq km, making Maine 3% larger than Serbia. Meanwhile, the population of Serbia is ~6.7 million people (5.4 million fewer people live in Maine).
Tip: This to-scale comparison of Serbia vs. Maine uses the Mercator projection, which distorts the size of regions near the poles.