What is the main job/duty of the executive branch?

The executive branch of the U.S. government is responsible for enforcing laws; its power is vested in the President. The President acts as both the head of state and commander-in-chief of the armed forces. Independent federal agencies are tasked with enforcing the laws enacted by Congress.

the correct answer is modern american cars are not available due to trade restrictions.

trade between cuba and the united states have serious restrictions. the u.s. imposed an economic embargo on cuba, that among other things means that modern american cars are not available due to trade restrictions.

in response to some governmental actions of the authorities from cuba, president john f. kennedy proclaimed an embargo on trade between both countries in february 1962. the trade embargo remains active until this day and was implemented directly by the departments of commerce and the department of treasury.

in president trump’s administration, there is a national security presidential memorandum that "strengthens the policy of the u. s.", affecting trade with cuba.