You might try unplugging the connector on the back of both headlamps and try turning on the high beams. If the fuse still blows, something has tangled with the cable between one or the other plug and the fuse that is blowing. If it does not blow, try re-connecting first one and then the other to see which lamp is causing it to blow, and you'll know which lamp needs to be replaced.
You don't say what year your coach is, so don't know where your fuses might be, or what access you might have to the back of the headlight modules.
Jim & Angie, Boise, ID
2006 Monaco Dynasty Countess III
2017 GMC Acadia Denali