All these guesses are great (except for the ones which suggest WW2 subjects
)
It could well be the DH.4, though I'd be surprised if that was produced as any other than a multi-kit project. At least two, for Eagle and Liberty powered types. In fact the Eagle was developed considerably during the war; though I don't know how much visible difference there was between early and late engines. And the DH.4 was fitted with many other engines at different times, Puma, RAF etc.
But the American DH.4 sounds like a good suggestion for this particular show.
If not the DH.4, maybe the SPAD XIII?
Now I'll offer my usual futile vote for a SPAD XII, or SSW D.IV, or something - anything - Austro-Hungarian...
Mark