Most likely, your original account was registered on the bitwarden.com server, and your new account was registered on the bitwarden.eu server. The two servers are completely independent of one another, so it is possible to have two accounts using the same email address (one on each server).
Whenever you log in to a Bitwarden app or browser extension, at the bottom of the first login screen (where you enter your email address), there is an option to select which server you are logging in to. You should ensure that the correct server is selected before entering your email address and clicking Continue.
To delete the old account, log in on the web vault using the correct server (most likely vault.bitwarden.com), then go to Settings > My Account, scroll down to the red box labeled “Danger Zone”, and click Delete Account.