Yeah, the highest nominal tax rate ends up being only a slightly-above-average effective tax rate, and probably a bigger deal than the slightly-above-average effective corporate tax rate is the significantly-lower-than-average benefit that US businesses get for what they are paying...

Having to pay for (compared to other developed countries, both expensive and inefficient) health care for employees on top of paying taxes for instance. Or the comparatively poor transportation, telecommunications, etc. infrastructure -- sure, its an annoyance to individuals, but its also a cost to businesses.

Its probably not a coincidence that the US has both a popular ideology which holds that government is fundamentally horrendously inefficient and an actual public sector that does far worse than other developed countries at providing value for the money customers are paying. Whichever happened first, the two obviously feed off of each other.