American Airlines typically arrives in area B. Iberian typically leaves from area D according to the airport’s website. Both are terminal 1 but it is one of the longest transfer distances without a change of terminal building.
Assuming you have checked luggage, the flow you will have to go through is: immigration checks, luggage reclaim, exit, go from area B to area D, recheck luggage, security check, hope that the plane hasn’t left. On two tickets, I declare this attempt thoroughly impossible with any hold luggage.
Assuming you have no checked luggage: I do not remember whether terminal 1 has any airside transfer paths and what the flow is. Considering my memory of how the area bays at Munich are constructed, I am leaning towards no. However in any case, you will definitely have to go through immigration and probably through a second security check in addition to somehow having to clear the distance between B and D.
If my assumption is correct and there is no airside transit at terminal 1 (I tried verifying this but the official airport maps are … suboptimal, and Google Maps, while being helpful, didn’t entirely confirm either side), I again call this an impossible connection, unless you are one of the first passengers to leave the aeroplane as immigration tends to get crowded quickly even on short haul flights with narrow-bodied aircraft e.g. from London – plus you cannot predict the queues at security and whether they will let you skip it. Immigration becomes more of a problem if you are not an EU citizen as they might ask you additional questions and the queue moves more slowly.
If my assumption is incorrect and there are dedicated direct lanes that bring you from area B via an immigration and a security check to area D you have a chance.
The above does not consider any potential delays your intercontinental leg may have.
If you make it within an hour, I would never again play the lottery as you have clearly used up your luck in that single hour.
Note: While I have used Munich airport often – and I thus thoroughly dismiss the assertion immigration control in terminal 1 be quick in any way, shape or form – I never had to transfer there as my home town is close to Munich. Thus my unawareness of a potential transfer path at terminal 1.