The car still could be highlighted at the Detroit show for VW.
The people who are going to be interested in buying this car in the USA are in California. It will still get the same publicity when it shows in Detroit next year. California is the car capital of the USA. I guess VW wants everyone losing their jobs in Detroit to drool over this car they would never want to have.
You have to look past who lives near the show, and more at the show itself.
Have you ever been to Chicago or the Twin Cities area during the summer? Convertibles actually sell really well up here, especially those equipped with hard tops, or folding hard tops (part of why companies like Volvo, VW, Chrysler, etc.. build them).
Regardless,
More buyers may be located in the LA area, but more media is going to be at Detroit (if history holds true). LA is slowly chipping away at Detroit's numbers, but currently NAIAS is still a larger event. I would personally rather attend the media preview at LA (as opposed to Detroit), however it isn't as cost effective for me to work freelance at that event, due to the smaller number of world introductions.
Look at the numbers
World premiers expected for LA this year 20+
World premiers expected for Detroit this year - 44+ (it is still early), and 14 North American first showings.