It can be a little confusing, but all our dealings with the Rotary Foundation tend to be in dollars as the targets and thresholds are set globally. There is only one Rotary Foundation and it covers the entire globe. The actual funds need to be held somewhere and that somewhere happens to be the USA. By paying funds into the Foundation, we are not 'sending money to the Americans', but contributing to a single global entity which supports Rotary Clubs in their work to 'Do Good in the World'.
In our part of the world, we can donate via the Rotary Foundation (UK) or RF(UK) for short. RF(UK) is a registered UK charity, which has a double benefit for us. Not only does it allow us to donate to the Rotary Foundation in Sterling, but it also allows us to take advantage of Gift Aid. All we have to do is to fill in a Gift Aid declaration and send it to the RF(UK) team in Alcester. They provide a reference to use for Standing Orders, or other direct bank payments, and they will handle all the paperwork on our behalf. RF(UK) act as a gateway to the Rotary Foundation itself, covering the exchange rate conversions and international transfers so that all the funds ultimately end up in the global account in dollars.