The 1998-2010 Multipla was never sold in the USA.
It was never certified to meet USA regulations (emissions, safety, etc.)
This is not because it was unsafe or had poor emissions, just that the regulations in the USA and Europe are different, and it is very difficult to make the same car meet both sets of regulations. Many manufacturers produce two slightly different specifications of cars, with different bumper, lighting and emissions systems, even when the cars look identical for the USA and Europe.
As Fiat was not present in the USA market when the Multipla was produced, there was no reason for them to produce a USA-regulation compliant version.
The Multipla is not old enough to be imported as an historic vehicle, so cannot legally be imported without meeting USA Federal regulations. Therefore there is no way, without spending the millions that Fiat didn't, to make a Multipla road-legal for the USA.
You might be able to import a 1956-1969 Fiat 600 Multipla (http://en.wikipedia.org/wiki/Fiat_600#The_Multipla_.281956.E2.80.931965.29) as a historic vehicle, but they are very rare. You are more likely to be able to find one in Italy than anywhere else, but even there they are very rare.
As far as I know its not available in the USA. The answer about it not meeting emissions regulations is just plain wrong - ir meets the latest European ones and so would pass in the USA if Fiat decided to sell it there..
No. Fiat would not make a profit to put a US emissions package on it and have it certified. Kinda like the old VW Beetles, dirty burning engine. Controls cost too much. Buy a HONDA!.They didn't need a converter in California until 1990! Every other car did in 1975!