United States is approximately 9,833,517 sq km, while Belgium is approximately 30,528 sq km, making Belgium 0.31% the size of United States. Meanwhile, the population of United States is ~332.6 million people (320.9 million fewer people live in Belgium).
This to-scale map shows a size comparison of United States compared to Belgium. For more details, see an in-depth quality of life comparison of Belgium vs. United States using our country comparison tool.