Country filtering in serch results?

Hosting is the main factor?

[financialhost]

From the UK our website lists very well in Yahoo.com - however when checking the same keywords based in the US with Yahoo.com the results are not the same, most often worse. I noticed the same thing on Google but it was not as noticable as Yahoo.

Our .com is hosted in the UK - is this the main factor involved?

I am thinking that changing to a US host would improve our listings for US users, which is a bigger market and we are an international business so would be better.

I have also used various proxies to check the listings and it seems that even in different areas of the US the results change - maybe Yahoo & others will boost local websites just a little but enough to make a difference in results.

Any solutions to this? Any advice?