backlash vs come about

backlash is a noun but come about is not a noun.

Word	Noun	Adjective	Verb	Adverb
backlash	Yes	No	Yes	No
come about	No	No	Yes	No

As verbs, come about is a hypernym of backlash; that is, come about is a word with a broader meaning than backlash:

Other hypernyms of backlash include fall out, go on, hap, happen, occur, pass, pass off, take place.

backlash (noun)	come about (noun)
an adverse reaction to some political or social occurrence
a movement back from an impact

backlash (verb)	come about (verb)
come back to the originator of an action with an undesired effect	come to pass