The White House has called on Congress to approve aid to Israel and Ukraine, but Republicans oppose any measure that excludes provisions to address security on the U.S.-Mexico border.
The simple answer is the worldwide weapons marketplace.
Basically all military weapons used by the US can only be bought by the government of the US by contract. So, you, as a country, can ask the US for weapons and buy them, like Taiwan does, and congress passes a bill to allow you to do that. Or, if you don’t have the money Congress passes an allocation to buy them for you, like Ukraine. US weapons are preferred, but you can also get cheaper Russian or Chinese. But the cost of those has strings attached.
The simple answer is the worldwide weapons marketplace.
Basically all military weapons used by the US can only be bought by the government of the US by contract. So, you, as a country, can ask the US for weapons and buy them, like Taiwan does, and congress passes a bill to allow you to do that. Or, if you don’t have the money Congress passes an allocation to buy them for you, like Ukraine. US weapons are preferred, but you can also get cheaper Russian or Chinese. But the cost of those has strings attached.