Before you call about being re-routed, look at your options on CO or other airlines. A friend & I were on a direct YVR-IAH this summer at 130PM , when they moved it up to 1130AM about a month before the flight. I was not able to get to the airport that early (due to a cruise). My only CO options were wait for a red-eye at 9PM or until the 1130AM the next day. I needed to work the following day, so both options were poor. The agent tried to put me on the red-eye, but I asked to go out on NWA's flights, connecting in MSP. They didn't hesitate and thanked me for knowing my options prior to them looking them up.

I just did a random Tuesday in January (not knowing when you're flying) and you can go
NWA: ANC-SEA-(MSP OR DTW)-MIA
Delta: ANC-SLC-PHL-ATL-MIA, or several others
Alaska: ANC-SEA-MIA

If you look on CO for ANC-MIA, there are several options through SEA & IAH or SEA & EWR, so that could work. I would recommend against EWR if the travel is this winter due to weather delays.