Welcome to the Q&A Forum

One possibility is that the level of competition in the us insofar as domain authority and inbound links for competitors is much greater than in the UK. Another possibility is that you picked up a good UK based link, which drove up those rankings. Has the site always been targeted in GWT to US?

Well, with search engines you do not want to be too many clicks away from the index page. 2 or 3 at most would be best. so if you can start out with a page that has no more than 100 internal links and each of those pages has no more 100. That would give you 10000 pages. Each would be no more than 2 clicks away. name each page graphics-design-richmond-va.html this would put all the keywords in the pages name. Which might help a bit depending who you ask. You can keep all the pages in the root directory. So you would have 10000 in the root. Some dont recommend this but Ive never had a problem.