What are the main reasons why US GAAP and IFRS differ?

A. US GAAP was developed to primarily satisfy the need of investors and creditors.

B. US GAAP was developed to primarily satisfy the need of tax authorities and government planners.

C. IFRS and US GAAP standard setters are operating in the countries with the same court and legal system

D. Cultural differences have no effect on developing multiple different standards in the world including IFRS and US GAAP