I don't think you know what
I don't think you know what you are talking about. The Fiat X1/9 and 124 Spider were always primarily for the US market. I am an Italian and it's very rare to see convertibles like this in Italy. People just don't have the disposable income for toys like this as in the US. I've seen maybe one X1/9 and a 850 Spider in two decades. People mostly buy hatchbacks and scooters. Same disappointment when Ducati owners don't see Ducati all over the place. It's because people buy scooters and use them as cheap city transport.
Hopefully the new 124 Spider sells better, but it's a very new car on the market, and Miata is an extremely well-established name in the US and certain areas of Europe (UK, etc). Also, Fiats dealerships are severely lacking in the US