You can change the home currency to USD on your own if the Multicurrency feature is not activated in QuickBooks Online (QBO), @Sirrah.
However, it's important to note that once the Multicurrency feature is enabled, modifications to the home currency are not allowed.
I've added a screenshot for reference:

If the USD is not yet available, I recommend adding this currency. A new subscription is required if you really need your home currency, as you will need to subscribe to a new account.
Here's how:
- Go to the Settings gear icon.
- Select Currencies.

Note: This option is available after you enable the Multicurrency feature.
- Select Add Currency.

- Choose the new currency from the Add Currency dropdown list.
- Click Add.

To know more on how to add currencies, check out this resource: Set up and use Multicurrency in QuickBooks Online.
You can also use these resources for guidance on assigning a customer's currency in QBO:
By following these instructions, you should be able to change your home currency. If you have any other questions about updating or managing your home currency in QuickBooks Online, we’re here to help.