The most accurate answer is that it depends on how you build and manage the sites. But if I had to guess I would say you are probably headed straight for trouble. Why do I feel this way? You are already talking about duplicate content & ranking issues instead of talking about how these sites are going to be providing unique value. Google does not copies of websites that all use the same content.
I know from my personal experience it is possible that you can profitably have multiple sites ranking at the top of the serp for the same keywords. I also know from my own experience that there is less reason for me to be launching multiple sites for the same industry.
Let's say you have really a good reason to launch multiple sites. Don't worry about using different Google WMT accounts, there are many other ways Google will quickly figure out you control both sites. Focus your efforts on building value & quality. You will need a significant amount of unique content for each site that is good enough to attract unique backlinks to both of your sites. Most webmasters launching multiple sites in the same industry don't do this and they tend to have very bad experiences.
Look into geo targeting if you want to stay out of trouble with multiple duplicate sites. You will want to send all US traffic to the U.S. site and all UK traffic to the UK site. You aren't going to have duplicate sites rank top 10 for the same keyword searches anyway.