The American government has the duty to buy US-made products, but the foreign companies still have the chance to become the supplier of US government. For instance, when one product is not made in US, the US government will buy overseas.
B.
The US government feels obligated to prefer US-made products, but it's still possible for a foreign company to be its supplier, for instance, if a product is not made in the US, then the US government will buy abroad.