Are both your servers in the same DC? On the same network? Does your provider support private networking between servers? If so, I'd start there. I'd disable outside access to your MySQL machine by only allowing the internal IP of the WWW server to communicate with it.
If your MySQL server is anywhere but local to your WWW server, then you will likely not gain much benefit from having to query across the country.
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If the server is not local (in the same DC) to your main server then this will actually degrade the performance/response times of DC quires and seek times. Get a server local to it, using an internal IP/crossover to the other server and cut out any outside connections to it. That will keep the server completely secure from any outside attacks. Make sure to use SSD drives with this mysql server too! If small enough just use RAM to load the database from, 10x faster.