After uninstalling PHPMyAdmin, account user still remains

Uninsalling phpadmin will not remove accounts from the mysql database. You can do that manually, but you would have to have root access.

You can recover root access with these steps.

From the terminal stop the mysql service, then load it without grant tables. In the steps bellow the text after the $ sign is the commands you input. The text in the parenthesis are explanations and comments.

(Stop the database)

$ sudo systemctl stop mysql

(Start Mysql without loading the grant tables)

$ sudo mysqld_safe --skip-grant-tables &

(Now log into mysql as root with no password)

$ sudo mysql --user=root mysql

(Set the root's password with:)

mysql> update user set authentication_string=PASSWORD('new-password') where user='root';
mysql>flush privileges;
mysql> quit;

(Kill the safe-mode server the "$" is the prompt. Hit the "%" and press ENTER)

$ %

Cntrl+c

(Now restart the database and you're all set)

$ sudo systemctl start mysql

Review this answer for details:
mysql don't ask for root password when installing