Illinois is about 4 times bigger than Guinea-Bissau.

Guinea-Bissau is approximately 36,125 sq km, while Illinois is approximately 143,961 sq km, making Illinois 299% larger than Guinea-Bissau. Meanwhile, the population of Guinea-Bissau is ~2.0 million people (10.8 million more people live in Illinois).
Tip: This to-scale comparison of Guinea-Bissau vs. Illinois uses the Mercator projection, which distorts the size of regions near the poles.