Fundamentally, if they can find a replacement at a lower cost, they will. Businesses are about the bottom line. No matter what their size is. Fighting that truism will only lead you to frustration.
This is not about the SF-based employees, this is about the roles the company has chosen to source in lower-cost regions. For whatever reason, they've decided that they are getting a lot of value out of local resources in SF, and some of that will be about being American, some of it about responsibility, some of it about liability and local laws that they can hold the employee to. When it comes to those roles they've based overseas, they've done for the sole reason of cheaper labor. If you stop being that cheap labor, they'll just hire someone else who is. If there is no cheap labor, then they'll hire a local in SF instead. It's really that simple, and I agree it's not fair - life isn't fair.
Fundamentally, if they can find a replacement at a lower cost, they will. Businesses are about the bottom line. No matter what their size is. Fighting that truism will only lead you to frustration.