Country-based Redirect on Homepage. Bad for SEO?

Hi Everyone

Couple of my sites(basic landing pages) were ranking in #1 spot for their specific keywords which were having low competition.

The sites were getting traffic mainly from US, France and Germany. So, I decided to display landing page in visitor country's local language with some country-specific and country-optimised content.

Say if visitor is from Germany, I would display him the homepage content in German Language.

So I wrote a simple PHP code using GEOlocation database.

The homepage just has following code :

if(country==US)
Load us.php
if(country==DE)
Load de.php

and so on.

Just after adding above code to both my websites, the websites lost their rankings in 3-4 days.

So, did the country-based redirect affect the rankings?

If that is the possibility, what changes should I make to make it more Search Engine friendly?

P.S. Its really important to me to display specific pages to specific countries as content varies depending upon country.

P.S.S. I have removed country based redirect and I am waiting to see what it does.