Anamorphic sets have been on the market in the U.S. since 1993. A small number of "squeeze" LD titles were included with some models, but never sold here separately. The majority of the released titles only came out in Japan.
http://www.lddb.com/search.php?adv_search=*&adv_reference=&video=1&picture=5
It's a safe bet the THX WOW demo was simply remastered for DVD.