I have never heard of serial numbers on bullets, and a google search led only to proposed state-level legislation to require them, which has not passed.
As far as I'm aware, no handguns currently being sold in the US employ microstamping. Also, I've never heard of serialized ammunition being sold in the US. Do you have sources on either of these currently being on the market?
California has a law requiring the use of microstamping on semi-automatic handguns, however, models previously certified for sale in the state are exempt. I do not believe any manufacturer is actually offering a microstamped firearm for sale.
The stamps are required to be on the firearm, not the ammunition. They're supposed to leave an identifiable mark on the ammunition when fired.