Why Fiat don't introduces new cars in the US?

Simple. Cars sold in the US must need US safety and emission standards. These standards are much higher than anywhere else except Canada (same as US). This adds extra costs. Fiat did sell cars in the US in the 60s, but had poor quality. Jokingly, Fiat stood for "fix it again, Tony" Renault attempted to sell cars in the US, but they were mired with poor quality. The exception is they designed the base for the highly successful Chrysler L series vehicles.

Those who claim that the emissions standards are weaker in Europe are wrong. In fact Euro standards for both fuel economy and emissions are much more rigorous than anywhere else (even Japan) and the US standards are embarrassingly low (except California). US cars (Chev, etc) that are sold in Europe may look the same, but are different. Same as the North American Fiat 500 looks almost identical, but has some differences. There must be some other differences in how each continent regulates its automotive industries that are coming into play.

They don't even have Lancia in Britain anymore and I'm gutted about it.

I believe the company does not to expand too quickly and end up with financial issues.

they are taking a big chance and the cars need to meet US safety standards.

The Fiat brand, in the USA, was known for shoddy build quality, the use of subpar materials, and expensive and constant repair needs resulting from cars they sold in the USA in the 1970s and 1980s that had all of those problems (and more). US buyers who remember those cars also remember the name on the front. Because of that, Fiat isn't just fighting to enter the US market as a newcomer - it's fighting to overcome its past image as well. A slower brand introduction where one proven Euro-market model (like the 500) is brought to the US market makes more sense than introducing a full line of Fiat cars to the USA because Fiat isn't sure that it can overcome its US image problems from the past.

They only make cars with the drivers seat on the right. But, they have been in production left hand drivers seat. Fiat was a bit scared that there car would turn out like the smart car. But I think the US needs the fiat small cars, there fuel efficient! the US safety standards of transpiration or more strict than most countries. The US wants to cut down on car crash and accidental deathes of the operators. To do this, the US can only bring cars with a 5.0 and above crash test result. But, I have been seeing comercials for these automobes on TV. Fiat is having a hard time reviving there "undependable" name in the US. Take for instance. The 1985 spider! I looks awesome, the front looks like a porche with the curved nose and the open headlights. But, these cars are known as a piece of crap mechanically. Although I too was interested. I wanted to buy a body and put a small VW emgine in it, just to make sure it would start every time. After 1990 I was surprised they didn't go out of business! But now they are competing with the other makes of cars. There engines are getting a lot more reliable too. Similar body sizes are the mini Cooper and the Volkswagen beetle. All that to say, Fiat should be making it's way to the US in the next 5 years. We wont have to wait to long.