Worldwide is not exactly a typical adjective. Things don't typically become worldwide. In fact, I can only find one example in the COCA:
1997 MAG AmericanCraft "...was originally invented in Japan about 300 years ago, but its use has become worldwide since the late 19th century."And I can't find any instances of seem worldwide. Nothing is ever *very worldwide or *more/less worldwide. It can be coordinated with adjectives (e.g., national and worldwide), but it rarely is (16 hits in the COCA for [j*] and worldwide). More frequently it's coordinated with PPs (e.g., in Canada and worldwide).
So perhaps it's a preposition. Both prepositions and adjectives can premodify nouns:
- the up button
- the from line
- the in crowd
Prepositions form the head of locational complements (e.g., she put it on the desk, he got it from her). Here, worldwide is namby pamby. You can't put something worldwide, but you can send it worldwide. You can't take something from worldwide, though I found one instance of attracting people from worldwide:
2008 ACAD InstrPsych "...database management to plan and implement the feasible strategies to attract all potential tourists from worldwide."Finally, we can look at it as a non-predicate adjunct. As adjuncts, adjectives require a predicate (e.g., Alone, he listened to Blur. not *Alone, there was Blur playing on the radio.) Prepositions, on the other hand, don't share this requirement (e.g., In the bedroom, there was a radio playing.) In this respect, worldwide is more like a preposition. But adverbs can also function as non-predicate adjuncts, so this really doesn't tell us much.
So you can see why I'm having trouble building a case either for or against worldwide as a preposition. Anybody have any better arguments?