Due to the history of the internet, anything ".com" should be assumed to be US-specific if not obviously global, just like anything ".co.uk" should be assumed to be UK-specific if not obviously global.

If you use a .com for something that is specific to a country/region that is not the US, the onus is on you to clarify. That's the problem here. If you're not going to make it ".uk", then you should be making that obvious on the homepage.

The US is the center of the world though. There are privileges to that like assuming the world revolves around you.