Having friends means that you can build bases where if you ask nicely, rather than having to invade. It prevents those friends from undermining you in a lot of cases. It makes them help you when you need, e.g. to get your hands on someone plotting attacks against you. It makes them more likely to trade with you under advantageous terms. I am sure you could think about at least a dozen other cases in a couple of minutes.

Soft power is spending pennies to convince other countries to do your dirty work.

Shape the world to benefit the US - having US dollar be strong primarily.

https://en.wikipedia.org/wiki/Soft_power

I believe Trump has asked that exact question. But also asked how much it costs and whether it can be privatized.

Make the dollar the global currency and reap the benefits of facilitating gentle commerce?

Did you forget the /s?

Some people mentioned the dollar as the global reserve currency, but there's also the use of English as the global lingua franca, the US being the largest global destination for talent and investment, and countries (previous) willingness to make sacrifices or deal with the US on less-than-perfect terms out of a sense of shared culture.