Enterprise Rent a car a total scam Edinburgh, Nationwide

We rented a car from Enterprise Edinburgh (Costorphine Road). After leaving the parking slot we perceived a funny smell coming from the engine. 10 minutes later smoke was coming out of the engine. We called for help and they told us to wait for almost 90 min. The cloud of smoke was so noticeable that people on the street were screaming at us that we should get out of the car as it could explode. 
We drove back to the rental place and a drunk mechanic (very Scottish indeed!) told us  that what happened to the car was caused by human error and that this happened hundreds of times with drivers used to drive on the other side of the road (ridiculous!) . I paid with platinum american express and thus I was covered by their insurance. However, they tried to say that human error was not covered and that they will keep the deposit until the mechanic ( the mechanic stinking of alcohol!) inspected the car and gave a report ( very reliable of course). I refused to sign whatever the costumer service employee wanted me to sign and called Amex right away who very efficiently got my money back. This was a scam for American tourists. When they saw American passport, NY drivers license and Amex they thought they would fool us. I do not drink and that gave me the advantage of being smarter than them. I would keep telling this story to everone I know.