I don't think an Italian surname would make any difference in the U.S. The majority of people I went to school with had Italian surnames and people never really erred away from English spellings for first names. No clashing IMO.
I would almost always side with
Michaela, simply because it's more familiar.
Micaela doesn't look "creative" but I am sure it would get misspelled rather often.
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"We are all horrible and wonderful and figuring it out." - Harris Wittels