Regarding B, why would you create your sock puppets in the US instead of in some developing country where everything is a lot cheaper?
If they are using it for 2FA it's likely for some US-only service.
"Authentic" US domestic resident sockpuppets for political or social manipulation. Combined with things like using residential proxies/relays through traffic on compromised routers on top-10 sized US last mile broadband providers such as Comcast, RCN. Google "residential proxies for sale" for some examples.
Plenty of things like the various services run by Meta will treat your content differently if they know you're coming from a Bangladesh phone number and ISP vs. being what appears to be an authentic domestic USA human.
Having live US phone numbers that can receive SMS for "is a live human receiving this code" verification purposes is also useful for many other kinds directly fraudulent activities.