Spellcheck stuck in Spanish

Just keep in mind that Language is a character attribute like color or font size, so Bill's solution might not always work if there are style overrides or text with no paragraph style assigned— i.e. you used Break Link to Style somewhere.

You should be able to change it by selecting English USA in the bottom of the Character Panel. If you set the language in the Character Panel with no documents open and then quit and reopen the program it will remain as a preference. If this does not work then check the language chosen in the Advanced Character Formats section of any existing Paragraph and Character Styles that you may have in documents where this is happening as well as the Basic Paragraph Style that may exist for all of your documents. I have experienced this problem in the past and found this to be the solution.