Please note the access query is incorrect!
It should be
UPDATE DISTINCTROW dbo_Employees INNER JOIN dbo_EmployeeTerritories ON dbo_Employees.EmployeeID = dbo_EmployeeTerritories.EmployeeID SET dbo_Employees.LastName = 'Leverling'
WHERE (((dbo_Employees.EmployeeID)=3));
This will only select records with EmployeeID = 3, with matching records in the EmployeeTerritories table and only process the same employee row once.
It is not correct to compare Access performance without writing the correct Access SQL.