I'd suggest dropping the title or, at least, drop the 'American' as there seems nothing distinctly US American about what you're writing and it's rather cliched.
The last line seems superfluous, particularly, "She didn't need an explanation".
>>what if the story was really about the father?<<
1. There's not enough ambiguity to even suggest that as a possibility. The piece is linear and only examines a very compact aspect of the relationship between mother and son - I know you're trying to get 'child' but again the observations made seem more stereotypically male(aggressive), probably due to narrative necessity.
or
2. Perhaps, re-title it as 'father?' - it would probably do more work for you than 'sacrifice' which is bolted into the story framework anyway and therefore makes its use, perhaps, tautological.
As it stands it still doesn't grab me - I'm not moved, interested, enlightened, engaged etc. by these people nor their circumstances, although there is a mote of sympathy for the mother.
Since your 'story' is short in length I might be tempted to rewrite this from several perspectives: the mother, the father, the doorman, the client(s) in order to explore those relationships and then, maybe, return to the original and see if anything useful could be injected back in.