Merriam-Webster's Advanced Learner's Dictionary
on \ ˈȯn , ˈän \
wrong \ ˈrȯŋ \
wander \ ˈwän-dər \
The American Heritage Dictionary of English Language
https://www.oxfordlearnersdictionaries.com/ (Former is British, Latter is American)
on /ɒn/ /ɑːn/
wrong /rɒŋ/ /rɔːŋ/
wander /ˈwɒndə(r)/ /ˈwɑːndər/
Oxford Learner's sticks to /ɒ/, while Merriam-Webster Learner's sticks to /ɑ/.
I wonder, for the British who want to pronounce the RP(Received Pronunciation) way, is the exact same /ɒ/ in these three words? For Amercians, is the exact same /ɑ/ in these three words?