What Fuse rating to use in a power entry module?
Yes, you can use a 240V fuse. The voltage is not relevant in such a case. Fuses are designed to protect over-current, not over-voltage. Therefore as long as the fuse is sized appropriately for your current and as long as your fuse voltage meets or exceeds your application voltage the fuse will safely protect your system.

The current drawn from a 120V source to power an 80-Watt device will be under 1A (2/3A) but for some devices you may want to consider a margin of safety for the initial power-on spike. 

In your case, it will be safe to use official 3.15A 240V fuses. It will protect the system from accidents just fine. If the initial power-on current is not very high, you can use 2A ones too.