July 2017 was the first month in which we could ascertain the year-over-year U.S. sales direction of the one-year-old Fiat 124 Spider.

That direction is down.

In fact, the rate of year-over-year decline — 124 Spider sales fell only 6 percent in a passenger car market that was down 15 percent — was by no means severe. But it’s yet another sign that when American roadster buyers want a Mazda Miata, they buy a Mazda Miata.

Miata sales increased for an eighth consecutive month in July 2017, a 13-percent uptick powered in part by availability this year of the MX-5 RF. Through the first seven months of 2017, Mazda’s Mazda is selling nearly three times more often than Fiat’s Mazda.

The 124 Spider, meanwhile, has seen inventory levels rise to uncomfortable levels as droptop season arrived in full and demand diminished. July’s 450 sales represented a four-month low for the Fiat convertible, but according to the Automotive News Data Center, FCA’s Fiat stores had a 102-day supply of roughly 2,000 124 Spiders heading into July, up from 84 days in June.

With few sales coming from the aged 500, the all-but-forgotten 500L, and the increasingly unpopular 500X, an additional one or two 124 Spider sales per dealer in an average month is of little benefit to Fiat’s U.S. efforts. Since its arrival last summer, the 124 Spider has produced 5,425 U.S. sales. Back on home soil, the 124 Spider sells at a rate of roughly 650 European units per month, about half what the MX-5 manages in Europe.

To be fair, the 124 Spider isn’t just a Mazda MX-5 Miata twin. Different engines are just the start. The cars are tuned to handle markedly different. And the 124 Spider looks, shall we say, different.

But it appears as though the 124 Spider may be different in the wrong ways. Unnecessarily immature ad campaigns won’t help, either.

[Image: FCA, Mazda]

Timothy Cain is a contributing analyst at The Truth About Cars and Autofocus.ca and the founder and former editor of GoodCarBadCar.net. Follow on Twitter @timcaincars.