To give you a short answer: When you book an AA award on a partner airline, AA's system give the Partner's system a shout saying "We need a ticket on this flight". It can take up to the aforementioned 24-48 hours for that processing to get done and back to AA before the ticket is issued and miles deducted. Sometimes it can be as quick as 30 minutes, other times it can be a bit longer.
Glad you got it sorted out!