Serbia is around the same size as Maine.

Maine is approximately 79,931 sq km, while Serbia is approximately 77,474 sq km, making Serbia 96.93% the size of Maine. Meanwhile, the population of Maine is ~1.3 million people (5.4 million more people live in Serbia).
Tip: This to-scale comparison of Maine vs. Serbia uses the Mercator projection, which distorts the size of regions near the poles.