My keyboard can plug into my phone through USB. It has an American key layout.
How can I switch its layout to another layout (like using Alt+Shift in Windows)?
Changing the layout of the on screen keyboard doesn't help.
Worst case, there's an app for that. Several, actually, but apedroid is well-reviewed, currently being maintained, and has a free demo version if you want to make sure it works for your set-up. $2-ish for the full version so "worst case" might be an overstatement.