A country can print as much currency as it wants. In that sense it cannot run out of money. What it can't do is print as much currency as it wants, and still have people want that currency, or have them accept it at the previous value. In that sense a country certainly can run out of money.

Take a step further back. As Thomas Sowell says, economics is the study of the allocation of scarce goods that have competing uses. In a free economy, money is how we organize that. But even if we had infinite money, that wouldn't give us more of anything else. It would just mean that everything cost infinite dollars to buy.

The problem that the Soviet Union had was that their economy couldn't produce enough to supply their military competition with the US. "Ran out of money" is one way of describing that, but the literal number of rubles in circulation is not at all the issue.