Whem I do an amended return on the website, does the IRS see it? Or does the IRS only see it if I mail it in? I wanted to amend it but now I don't want to.

No.  Only if you mail it in.  So if you haven't mailed it nothing happened.  Do you want to undo it?

You can delete the amended return this way.  Do the steps slowly and carefully.  After you delete it then you need to manually take out the changes you made to put your return back to the original return.

How to delete an Amended return in the Online version

https://ttlc.intuit.com/community/amending/help/how-do-i-cancel-or-undo-an-amended-return-in-turbotax-online/00/26315