Based on a very quick scan, you can get the following (I'm actually a little surprised at the availability):

Out
15 Jan: JL and BR each have one seat in C
20 Jan: JL, BR, and CX each have four seats in C

In
2 Feb: OZ has five seats in C

These are only in the trans-pac flights, I didn't have time to go into the detail of connecting C availability, but each of these will eventually get you to/from SGN in award seats. I also didn't check SkyTeam, but this is pretty much it for three days either side.

I don't know about the Amex transfers in the US for these...