Why Didn't America Adopt the Metric System?

Every country in the world adopted the International System of Units (SI) except the United States, Liberia and Myanmar. But why? America still uses English or Imperial system of units the isolation from Europe and vast sales locally may be the reasons.

Feet, yards, inches, miles, gallons, ounces, these may mean something to some people around the world, while others struggle with online converters or, worse, software designed to convert these values, that are not reliable most of the times.
How about fathoms, rods, chains, furlongs, leagues?
Only 3 countries don’t follow the metric system of units and they are the U.S., Liberia and Myanmar, every other country since the 1960 follow the International System of Units (SI) ("Systéme International d'Unités" in French, hence "SI"). Metric units of mass, length and volume are widely used around the world for everyday use as well as for business and scientific purposes.
I have this problem, whenever we deal with Europe, we have to convert every unit. Once complete, the converted units don't make any sense to me and I have no way to quantify it anymore.
So why didn't the U.S. move to the new SI Unit system when the rest of the world did?
Initially, officials believed it would be an too cost prohibitive to convert everything at all U.S. manufacturers. But now, many products are made overseas and imported; America has become more of a service-oriented economy rather than an Industrial-manufacturing economy. In today's world, converting to SI units would not be a big problem.
According to a reader on Softpedia, Europe adopted the SI system in 1960 to make trading between European nations easier after World War II, a world from which the United States was isolated.
There was a debate in the U.S. to move to the metric system in the 70s but manufacturers said they were comfortable having their own system. The world also saw the advent of HP calculator, making unit conversion easy. The metric system, again failed to get traction in the U.S.
Today, conversion is even easier: with the presence of Google, you can convert units incredibly quickly (here is a sample calculation in Google), meaning there is still no real reason to switch.
But not all Americans agree. NASA has recently agreed to used metric systems over English system of units.
The decision was made because the metric system offers a lot of convenience: It provides a single unit for any physical quantity, thus eliminating the need for conversion factors and making calculation easy and direct; multiples and submultiples are related to the fundamental unit by factors of powers of ten, so that one can convert by simply moving the decimal place (i.e. 1.234 meters is 1234 millimeters, 0.001234 kilometers etc.), whereas the English system of units cannot be used in the same way (i.e. 1 lbs = 16 ounces)
Even with all of today's conversion calculators, changing units from the English system to SI units is a laborious process and, in many cases, you end up with errors. Furthermore, it can be incredibly time consuming (I was recently preparing a report for an aircraft manufacturer that wanted SI units, which ended up taking me hours to change all numbers correctly).
This article gives a few examples of converting units to illustrate the unit conversion problem:What is the mileage of a car that uses 8.7 liters of fuel per one hundred kilometers? What is a pressure value of 174 pounds per square inch transformed to kilograms per square meter? How much is a density of 1.6 grams per cubic centimeter transformed to pounds per cubic foot?Times have changed, and I think America now needs to switch. If we have one system of units, it will make worldwide trade easier, we will be able to communicate properly, and essentially all speak the same language.
Would you like to have one system of units or you like the way it is now?