The short answer: it does not need to affect your SEO result if you set things up correctly.
The long answer (according to google):
Google's goal is to return the most relevant and useful sites in response to a user query. As a result, the results we show to a user in Ireland may vary from the results returned to a user in France.
If your site targets users in a particular geographic location, you can use our geographic target tool to provide us with information that will help us determine how your site appears in our search results, and also improve our search results for geographic queries. This data supplements our existing information, and setting a geographic target won't impact your appearance in search results unless a user limits the scope of the search to a certain country.
You can only use this feature for sites with a generic top-level domain, such as .com or .org. Sites with country-coded top-level domains (such as .ie) are already associated with a geographic region, in this case Ireland.
If no information is entered in Webmaster Tools, we'll continue to make geographic associations largely based on the top-level domain (e.g. .co.uk or .ca) and the IP address of the webserver from which the context was served.
If no information is entered in Webmaster Tools, we'll rely largely on the site's country domain (.ca, .de, etc.). If an international domain (.com, .org, .eu, etc) has been used, we'll rely on the IP address. If you change hosting provider for a country domain, there should be no impact. If you change the hosting provider of an international domain to a provider in another country, we recommend using Webmaster Tools to tell us which country your site should be associated with.
source: google
Video on Google SEO and Geo tragetting; http://www.youtube.com/watch?v=r9r3PayqaZM
