Not a lot of Passat TDIs were sold here. Imports were limited by corporate average emissions standards. IIRC there were about 6,000 sedans sold in '96-7, and about 1,200 Wagons. Keep in mind this is over 20 years ago, and that the Passat isn't a terribly expensive or desireable vehicle (except to us) so they weren't necessarily well cared for. Most are worn out or rusted out by now. I was at a TDI gtg recently and asked a group of people when they last saw a B4 Passat on the road. Only one of the 8 or so people I was talking to could even recall seeing one in the past year.
We still sell a fair number of parts for these cars, but I believe the remaining vehicles are owned by enthusiasts, many of whom are TDIClub members. And lots of parts for these cars are going obsolete. I talked to a customer today who was looking for a lower radiator hose for his B4. No longer available. Door handles? Nope. fuel lines? NLA. You get the idea.
I like these cars a lot, but when I drive mine I am aware of its age. The difference between a B4 and a MKIV or B5 VW is dramatic. Still, they're strangely appealing cars. And the range is hard, if not impossible, to beat.