The war wasn't fought in the USA. The USA suffered a great deal less than Europe in WWII as well because the war was not fought there. Not to mention that the Vietnam war was a civil war which started before the US got involved, and continued after.

So yes, OF COURSE Vietnam suffered more.

And even before that, Vietnam was fighting another war with the French. A war that ended just one year before the next war started. And before that, the French had occupied Vietnam for several hundred years although they were not at war.

Vietnam hasn't suffered from just one war. Vietnam has suffered from hundreds of years of occupation by other nations, fighting wars both with and against those nations. Vietnam has done a TREMENDOUS job building itself up in the past 40 years since those wars and occupations ended.

I'm not an expert on GDP, but Vietnam is more developed and has a higher quality of life than Cambodia or Laos. Life expectancy in Vietnam is higher too.