The below Gallup polls are for the USA.
More Americans have thought a third-party is needed, than think the "Republicans & Democrats are doing an adequate job" ever since 2006.
Independents are more unsatisfied than Democratic & Republican party members (I guess unsurprisingly) but even among Republicans (the most satisfied group) between 30% and 52% have thought "inadequate" ever since 2006. Relevant to reading that second graph: the makeup of the US is roughly 1/3-1/3-1/3 (self-described) Democratic-Republican-Independent as a rule of thumb; here are more precise estimates:
But despite that, only a tiny percentage of Americans vote third party. This enormous inconsistency is the fault of our plurality voting system.