Why can't a country print its own money to spend it only abroad? If a country prints money and distributes it between the people, it causes inflation. But what if a country prints its own money to spend ONLY abroad, which would allow a country to buy whatever it wants. What's wrong with this logic?
This wouldn't work - for the money to have any value abroad, it has to find its way back to the source country.

Consider an example; the President of Ruritania wants a Swiss watch. He prints a thousand Ruritanian dingbats and sends them to his ambassador in Bern with the instruction to buy him a watch. However, the Swiss watch-maker doesn't want to be paid in dingbats - he wants Swiss Francs. So the ambassador goes to a Foreign Exchange (Forex) broker and asks to buy Swiss Francs using Ruritanian dingbats. What rate does the Forex broker give him? The broker has to consider what he could do with the dingbats - all he can do is sell them to some Swiss guy who needs dingbats for some reason. So it's the demand for dingbats in Switzerland that determines the rate.

Let's assume the Forex broker gives the ambassador some Swiss Francs and off he goes and gets the watch. What happens next? The broker sells the dingbats to a Swiss importer who is buying Ruritanian apples. The Swiss guy uses the dingbats to pay his supplier in Ruritania and now, the dingbats have ended up back in Ruritania!

So the Ruritanian money supply has increased and, despite the best efforts of the President, inflation is stoked.