I can’t tell the difference between han Chinese and Korean and Japanese

That is because the diversity within the han Chinese genepool is so vast that it actually surpasses and even contains the japanese and korean genepool. That's why japanese look very similar to each other but han chinese can be divided into different groups that are sometimes even considered different (like the hui, southern han, taiwanese) etc. It depends which genetic markers are examined.

your typical American and they would probably see 3/5 of them and say Chinese, and would probably say Arab/Indian for the other 2.

the typical american or human in general is not very educated

None of them look Caucasian as defined by your typical American (North Atlantic/Nordic/Western Europe/ Slav)

like I said european is not the same as caucasian. there are simply too many variables.

Greece, Levantine Arabs, or Turks given that these are probably the three most “ethnic” groups that can pass as white.

Imran Khan looks like a Lithuanian even though he is 4,498 km away. meanwhile some polish people look like mexicans.

it all has to do with bone structure. the thing about greeks, levantines, and turks is that they have red sea ancestry and basically look like jews (mediterraneans). caucasian doesn't really refer to mediterraneans but to the population that originated in ukraine/kazakhstan and then diverged.