It refers to a fairly new american politically correct term that replaced things that people who are usually called asian get called. In making things less offensive they decided on a word that is overly broad and not very specific or well thought out.
In general terms most people I know would take it as a replacement for what most people would in the past have unsubtly labelled "CHINESE".
Where "chinese" would refer to anyone with straight black hair, slanted eyes, and a tan. ie. a yellow person. The actual origin would not really matter, anyone with that description would be labelled (until corrected otherwise)"chinese" , be they from: china, japan, korea, vietnam, laos, phillipines, indonesia, brunei, malaysia, cambodia, myanmar, bhutan, nepal, etc. It also replaced the slightly more descriptive "oriental" (which also would technically covered asia but was more easily understood to be the areas east of the himalayas.
Asian would commonly now refer to anyone east of Persia in general, so it is sometimes confusing...although I think most white people in north america would refer to the subcontinent as generically "Indian" or a "paki(stani)" independent of what bearded country on the subcontinent they came from. Rather than Asian unless there was a large group of "foreigners" being referenced. In Canada this would also probably be closely followed by some sort of derogatory but common phrase along the lines of "like woowoo Indian or (insert simpsons Apu accented catch phrase) Indian"
Everyone West of the subcontient would be generically refered to as a muslim, arab, or more derogatory term depending on the speaker (persians would be in that mix mistakenly or not).
Israelies would be jews or israelies.
Turkey would not even be thought of at all actually and definitely not as part of asian, as they are generally pretty much white in North America.
As far as the pacific islands...the people there would probably depending on the look either be wrongly generically labelled chinese if they look Han, or maybe hawaiian, or maybe mistakenly "Indian" (meaning "woowoo Indian in this case).
Tried to be specific and realistic as possible without too much offending...that is pretty much how it works in the real world.