Which country exports the most oil to the US?

It is not Saudi Arabia, it is Canada. Canada imports about 1,950,000 barrels a day, (about, an average :) )

while Saudi Arabia imports about 1,000,000 barrles a day.

Source:

http://www.eia.doe.gov/pub/oil_gas/petroleum/data_publications/company_level_imports/current/import.html