Taxes for USA expats can be complex. The USA is one of less than a handful of countries that tax citizens on worldwide earnings no matter where they live.
If you are employed by a foreign company and stationed overseas for the full year (in qualifying countries) you will pay tax on your earnings where they are earned and have the first $100,800 (in 2015) of earnings excluded from USA income tax. However earning above that level will be taxed where you earn them and by the USA. Learn about the Foreign Earned Income Exclusion on the IRS web site.
Like banking, taxes (at for USA citizens) are one of the more difficult issues of an overseas (including nomadic) lifestyle.