Answer
Citroen and peugeot are french and are now part of the same company, fiat is italian.
citroen cars have had a difficult history in the us, the low point being in 1974 when the cars were banned after the three main us manufacturers used their oligopoly powers to force citroen from the market. the reason was that the citroen cars did not comply with all of the specification requirements in place at the time (for instance, the type of headlights or fenders that were supposed to be used). other than some independent importers who have continued to bring
small amounts of citroen cars in the country, the company does not seem to have ever approached the us market since 1974, probably due to poor economics.
peugeot sold cars in the us for 33 years through to 1991, but quit the market at that time due to poor economics.
the fiat group owns a number of brands that are sold in the us, including ferrari, maserati and alfa romeo. they have also, in the past, had a partnership with us car maker, gm, but this was dissolved in 2005. it is
reported that fiat is now courting ford for a similar partnership. however, the cars under the main fiat brand do not appear to have any dealerships currently in the us.
for all three brands,
peugeot and fiat, there are a number of service centers and parts dealers in the us. so, should you decide to try to import one or to buy one from ebay, you will have a way to keep the car on the road.