Thanks for posting. :)
There are some handy customizer apps which offer printing on mugs, and may be able to help you out. I've included links to some of these below, which you may like to consider:
Though some of our other forums users may be able to suggest manufacturers operating from the US too.
Hope this helps you out!
Koreen W | Shopify
I am based in the UK and am a ceramic designer and maker. I frequently ship my mugs to the USA so I am sure I can help you.
Please have a look at my website for further details.