Financial Infographics has posted and infographic comparing the tax rates of nations around the world. The U.S. Federal rate varies from 15% to 35%. This does not include, however, any additional rates that the state, or even city, may impose. What may surprise you, is that the first income tax in the United States was in 1812, to finance the war against Great Britain.
It would be interesting if regulations where also included. As they are also a tax (making it more costly to do business). When a business decides what country they what to be headquartered and only looks at the tax, he might find a mountain of regulations to deal with making it a lot more expensive to deliver their goods/services.