Guam is about 204 times smaller than Cuba.

Cuba is approximately 110,860 sq km, while Guam is approximately 544 sq km, making Guam 0.49% the size of Cuba. Meanwhile, the population of Cuba is ~11.0 million people (10.8 million fewer people live in Guam).
Tip: This to-scale comparison of Cuba vs. Guam uses the Mercator projection, which distorts the size of regions near the poles.