Why is Vietnam more cheaper than the USA?

Besides the fact that labor is much cheaper in Vietnam (which I don't think is the main reason things cost less). Vietnam does not have lawyers suing every company that manufactures a product or delivers a service. Over here, if a company injures someone, the director and those responsible are given huge fines (ie the government takes all their money) and either imprisonment or execution. Wall Street executives would have a very short lifespan over here.

Vietnam also does not have a dozen or so government agencies that inspect/safeguard products like the US.

Those are some of the reasons. I still don't understand why I can buy a pack a Wrigley's gum for about a nickel or a bottle of Pepsi for a dime. I think companies charge more in America because Americans can afford to pay more.

people work for less, so they can sell the products for less

"cheaper" not "more cheaper"