Actually they passed Toyota recently. GM used to be #1 for decades in total sales, then Toyota passed them. Just because they're the largest and have been doing it for a LONG time doesn't mean they make the most reliable cars. VW and GM are prime examples of that.
VW sales are also very low in the US:
June 2015: Cheap Gas Moves More Metal Edition, but (VAG) surprisingly high for rest of world.
JDPA's "long term reliability" is hardly "long term". It's their VDS that only looks at 3 year old cars (length of basic warranties on most cars is only 3 or 4 years):
2015 Vehicle Dependability Study | J.D. Power. I highly doubt that most people in the US only keep their cars for 3 years given that the average US vehicle is now 11.5 years old:
http://www.usnews.com/news/business/articles/2015/07/29/average-us-vehicle-age-hits-record-115-years
I don't think that's correct re: "Most Volkswagens in the US were built in Brazil for many years". Many were coming from Mexico.
As for "I think a very large number are built in the US now..." not really. The ONLY plant they have in the US is the one in Chattanooga, TN and it ONLY builds the Passat. Per
VOLKSWAGEN OF AMERICA REPORTS JUNE SALES GAINING 5.6 PERCENT OVER 2014 : Volkswagen US Media Newsroom, Passat made up only 24% of VW-brand sales in the US. They plan to produce an SUV there but that won't happen until end of 2016:
NEW MIDSIZE SUV FROM VOLKSWAGEN TO BE PRODUCED IN CHATTANOOGA : Volkswagen US Media Newsroom
VW also traditionally has done poorly in Consumer Reports reliability surveys. And, it seems I know WAY more people w/unreliable VWs than those w/unreliable Toyotas and Hondas, despite the low % of VW sales in the US.