iMac showing US international in upper right corner. Will not let me log in.

Hi,

Try to start up in Safe Mode, then normal boot which could solve your issue.

https://support.apple.com/en-us/116946?displayMode=headless&linkId=100000352907239

If it doesn't help, try the following tips which could solve your issue.

To resolve the "US International" issue and log in, restart your Mac and press and hold the Option (⌥) key on your keyboard when you see the Apple logo or hear the startup chime to open the Startup Manager. From there, select Recovery from the options, and then use the Disk Utility to repair your startup disk and reinstall macOS if necessary. You can also click the keyboard icon at the login screen to switch to your primary language, if available. 

Can’t you just Click on that us international icon and choose a different keyboard, like US?

What year model iMac and what macOS version is it running..?

see > Identify your iMac model - Apple Support

What keyboard and mouse do you have...?

If you have a rechargeable Magic keyboard, connect it to the iMac using the supplied charging cable.

If not, dig out, borrow or buy an inexpensive USB keyboard and mouse to get logged in and reconnect the wireless one.