Sure. California, Texas, New York doesn’t make residency a requirement. Think about all the illegal immigrants in those states. They need the vaccine too. https://flytrippers.com/getting-vaccinated-for-free-in-the-usa-our-first-impressions/
You would get it at a pharmacy like in the post above.
So my advice is book TPE - SFO, chill for a day, then go onwards to Canada. Or if you have a long layover (4.5hrs plus) you can probably find a pharmacy in San Mateo (where SFO is) to get the vaxxx.