In the US, "fiat" usually refers to traditional government currencies, such as the US dollar, which is controlled by the central government. To better understand the difference between fiat money and cryptocurrency, I recommend reading the explanation here: https://paybis.com/blog/glossary/what-is-fiat/ — it describes in detail how fiat works and why it differs from decentralized assets. When making transfers in the US, it is important to take into account the conversion rate and bank fees in order to minimize losses and plan your budget correctly.