Hope your Drupal is set up correctly, I recently migrated a site away from Drupal to a more flexible CMS, the Drupal installation created a 5gb+ database for just 150 pages of web site and regularly crashed! As others have stated you need to watch how Wordpress is set up as well.
North America - you have plenty of hosts to choose from, some dire, some truly excellent
If downtime is an important factor then you need to be looking at a better quality host, and probably upping your budget a bit. If you get traffic spikes again you need to work with a host who won't just suspend your account if you go over quota all of a sudden, and one who's servers can cope!