Issue with album art I added to iTunes not showing in iPhone and iPod Touch

I searched online to find a way to add missing artwork to my iTunes library. (I tried adding the art letting iTunes do it and for one album, it was still working on it two hours later. I can't wait forever.) I followed the suggestions saying to copy the artwork either from Amazon or doing an online search using the title of the album. I had no idea when I did this and followed through with adding it to my iTunes library that the art photo would be to large in size (pixels) and wouldn't show up on my iPhone 14 and iPod touch 7th generation. I added the artwork directly to iTunes library without either device connected to iTunes. Now I have the cover art in the actual iTunes library, but it will not show up on either iPhone or iPod. How do I go in and delete the album art, not the album itself. All the work I spent searching and adding artwork has been for nothing.

Is there anyway to correct this? Or do I just have to live without the artwork on my devices? I do not want to go through erasing my entire music library that I added to iTunes. Most of the albums were added to iTunes years ago.

Please advise.

Thank you.