To a computer, "North", " North " and "NORTH" are three different regions. Filters miss rows, groups split in three, and lookups fail. Text cleanup fixes that before anything else happens.
- Transform > Format > Trim removes spaces at the start and end of each value.
- Transform > Format > Capitalize Each Word (and lowercase, UPPERCASE) makes capitals consistent.
- Home > Replace Values swaps one value for another. Tick Match entire cell contents to replace only cells that are exactly that value.
Trim first, then fix the case: a value with a leading space would otherwise keep it. Select the column header before you choose the command, so the step changes only that column.