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Query regarding international transaction between governments 
Buyer A didn't send money to the US government, Buyer A sent money to Seller B, a US resident.  I think the most common way to facilitate a transaction like this is a regular old international wire transfer. Buyer A in India goes to their bank to exchange X INR to $1mm USD.  $1mm USD is then wire transferred to Seller B's bank account.  The USD was sold to Buyer A, either by funds held by Buyer A's bank, or foreign exchange markets, or possibly the US government.     Seller B may owe taxes on the gain derived from the sale of this thing to Buyer A, but that taxation would arise regardless of who the buyer was.  Buyer A may owe an import tax in India upon importing whatever they bought.  I don't think it's common to tax imported money in this sort of transactional setting though.