I'd say it's more like 'ci' (sounds closer to 'ty') in Italian 'ciao' and less like 'ch' in 'change'.
In American English (and perhaps other dialects), Italian 'ciao' is an allophone with English 'chow'. (Really two allophones, 'ch' and 'ow'). Most Americans won't be able to hear a difference.
"ciao" and "chow" are homophones, not allophones. Allophones are different phonetic representations of the same phoneme found in complementary distribution. For example, [t] and [th] and [ɾ] and [ʔ] are allophones of /t/ (the first in 'cat', the second in 'tack', and the third and fourth in 'cutter' , depending on your regional variant. Also, the initial phoneme in Italian "ciao" is for all purposes identical to the one in English "chow" (the vowels are a bit different) - it is written as: /tʃ/