Subsidies are also expensive for the tax payer. Warping the market costs money. (No comment on whether it's being warped in the "right" way right now.)
Having the world reserve currency is an independent source of revenue for the US Government, as it allows for an amount of monetary inflation without corresponding price inflation. Through a combination of Federal Reserve policy and the political martingale of "balanced budgets", most of this revenue has been simply given away to asset holders in the form of low-interest loans. This money could/should instead be spent to purposefully mitigate the damage to domestic industry that comes from having the world reserve currency.
