Vietnam is about 1,871 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Vietnam is approximately 331,210 sq km, making Vietnam 187,024% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (103.2 million more people live in Vietnam).
Tip: This to-scale comparison of District of Columbia vs. Vietnam uses the Mercator projection, which distorts the size of regions near the poles.