Yes of course, subject to availability.

Booking codeshares is where it gets dicey. Availability can be different and there might be traffic restrictions that prevent you from booking a particular codeshare unless it connects to an international flight. Or in some other cases, it's the opposite - some can only be booked with a stopover. It's pretty random and unless you have access to a GDS there's no way to know in advance what the rules are going to be.

Additionally, for AA metal the AA RTW desk will only book you on the prime (AA) code, and even for non-AA-operated flights some agents might require some convincing before they'll book you on a codeshare. (Usually mentioning that you're not crediting to AAdvantage helps)