a squib, not having much of an explosive effect to begin with, becomes even less efficacious when damp:

[Of obscure origin; perh. intended as imitative of an explosive sound.]
1. a. A common species of firework, in which the burning of the composition is usually terminated by a slight explosion.
‘Squibs are straight cylindrical cases about 6 inches long, firmly closed at one end, tightly packed with a strong composition, and capped with touch-paper’ (1886 Encycl. Brit.).
...
d. fig. or in fig. contexts. damp squib, something that fails ignominiously to satisfy the expectations aroused by it; an anti-climax, a disappointment.
1847 Alb. Smith Chr. Tadpole i. (1879) 20 The literary gentleman having finished, like a damp squib with a good bang, resumed his seat. 1963 Times 6 Mar. 11/3 Possibly because too much was expected of it, the long-range study of Britain's transport needs by a Ministry of Transport group under Sir Robert Hall is something of a damp squib. 1976 Yorkshire Even. Press 9 Dec. 8/5, I came here thinking this Scarborough business would cause fireworks, but I have never known such a damp squib.


(OED2)

I'd say that it's not heard much in the US, outside of the military.