Perfect candidate for geo-targeting! You can keep them on one domain though if you're interested. You can do subfolders and geo-target each, but not sure if that works with your setup. Regardless, if you do the .com, and want that to be US only, make sure to claim that domain in GSC and Bing WMT as the US. .com is a general TLD, so it doesn't auto-geo-target. ccTLDs like .co.uk do automatically take care of this.
Keep in mind that in best practices, if you have two pages with the same content across two domains, usually the SEs will pick one, the older stronger one. Try to find a way to differentiate the content that is the same across the two sites. You can also use hreflang between the two sites to help the association, but that is really meant for translated content only. However, people have seen it help.
To ensure people are getting to the right content, I recommend detecting the user's location by IP and ASKING if they live in the US, UK or others you might geo-target. Then set a cookie. They will always get to the right content. Google will crawl from the US, ignore the JS for the most part, and will index everything.
Think about the .com and subfolder idea, that might be better for you.