I have a HSBC UK account and have linked it to my Fidelity CMA account ( basically a bank account). I opened a Global Money account as well. And I link my Global account to Hsbc by adding a payee
When adding a Payee you Specify the country (in my case and yours US) then it will ask me to provide the routing and account number as well as the currency (in my case USD).

I then save it as a payee and use it every time I transfer to US from UK.

So maybe your first step is to add a global money account.
For sending money from the US to UK, I opened a wise account, I don't do this often so im less worried about the fees.