[Fade_Dance]

FX necessarily trades in pairs. To buy a peso one needs to sell something against it, and the US will sell dollars if acting in the FX space.

Since the USD is one of the core currency crosses and is at the base layer of the financial system, raising the peso/dollar cross is effectively strengthening the currency against all other currencies.

Also, while the specific political circumstances around the pesos swap line are dubious, the US often extends dollar swap lines to other central banks. The other side of the privilege of having the world reserve currency is having the obligation to support the stability of the world financial system (although this example is more off the wall than the typical example).

[bigbadfeline]

> raising the peso/dollar cross is effectively strengthening the currency against all other currencies.

If the peso rises against all other currencies, the dollar paying for it must fall against them, not as much but the dollar falls - at least relative to the movement it would experience without the purchase of pesos.

> Since the USD is one of the core currency crosses and is at the base layer of the financial system,

Abracadabra isn't an argument.

[sdwr]

Right, and the US (presumably) has the mass and stability to weather that impact much better than Argentina does.