I know we are way too late for this, but why did your company decide to internationalize the site structure if you can't get localization resources. I would have suggested using cookies and JS to set the currency, etc.
Anyway to your questions:
Or am I chasing ghost and this rule won't change much in the eyes of Google and my ranking? You can implement the title rule above, but I don't think it is going to help much.
**I don't care so much if US content shows up in the UK in term of content though are eCommerce experts would be quite pissed off as it would biased reporting. **
I recommend setting up IP location detection. If the user SEEMS to be in a different country, ask them if they are from the other country and if they say yes, then redirect them there. Don't assume they are in a specific country though.
Focus on getting those resources, you won't make a big impact without them in a high competition area.