IMO I think for right now anyway they’ll focus those aircrafts for short haul out of MIA. If anything possibly the 321neo could be used for translantic service as a replacement for 757.
That wouldn't surprise me. Especially since they'd need to reconfigure the 7M8s from their near-cattle car configuration right now (172 seats). I wouldn't be surprised if they used the A321neo on some TATL flights. That'd open the door to a few new European destinations, like BHX, BFS, CPH, WAW, AGP, GLA, and VIE. And I don't even include KEF and MXP on that list because I think those are do-able on a 752 and 788, respectively.
AA is already using this junk to Brasilia and Bolivia. That's just as far as Europe from the Northeast. They are now a budget, no frills, no service airline, so wouldn't surprise me to see them used to Europe.
I do recall hearing that. Both MIA-BSB/VVI have a 7h 40min block time and is roughly ~3,600 miles. By that logic, AA could add BRU (3,760 miles), AGP (3,730 miles), OSL (3,750 miles), BHX (3,450 miles), GLA (3,300 miles), BFS (3,250 miles), OPO (3,400 miles), ORK (3,190 miles), KEF (2,690 miles), CWL (3,420 miles), and PDL (2,630 miles) with the 7M8. Any thing past that is a stretch for the 737MAX, so places like WAW, VIE, and CPH would need a different aircraft.
As for the A321neo, FRA (3,930 miles), CPH (3,920 miles), GVA (3,940 miles), MRS (3,990 miles), DUS (3,820 miles), PMI (3,990 miles), and HAM (3,890 miles) are all within reach of the A321neo.
As for any of these routes actually happening will remain to be seen. BRU seems likely if AA were to send the 7M8/A321neo overseas. That's a big hole in their European network, IMO. Considering PHL is their largest hub for transatlantic flights, KEF seems likely eventually. It confuses me as to why they started DFW-KEF instead of PHL-KEF. A summer PHL-GLA seems likely to eventually happen. Both DL and UA fly there in the summer, too. AA has been shrinking in Germany as of late, dropping PHL-FRA/MUC recently. They also tried DUS a few years back but it didn't last long. I don't think AA will try anything in Germany for a while. That's also partially due to the fact that LH/UA/Star Alliance dominate the US-Germany flights at the moment. So I don't see FRA/HAM/DUS happening for a while. CPH is a similar story. Dominated by Star Alliance carriers, and mainly SK. DL does fly there from JFK in the summer so who knows. This one seems like something US could've pulled off when they were in Star Alliance, but not anymore. GVA also falls in the same category of Star Alliance domination. AA only has 1 daily flight to anywhere in Switzerland, with that being a daily PHL-ZRH. UA/LX have a pretty good stranglehold on the US-Switzerland flights at the moment, so I doubt GVA is happening anytime soon. DL launching JFK-GVA seems significantly more likely that PHL-GVA. WAW/OSL are also big Star Alliance markets, so my bet is any growth there is from UA. EWR-WAW on UA seems likely eventually. As for, AGP, BHX, BFS, CWL, OPO, ORK, and PDL, I just don't see enough of a pull for those markets to work. AA/DL/UA have all tried XXX-BHX in the past and none of those routes remain. UA ran BFS-EWR a few years back but that's gone now too. I don't believe any of the US3 have ever tried CWL/ORK. DL runs JFK-AGP/PDL and UA runs EWR-OPO, and I doubt there's enough demand for 2 transatlantic flights, even in the summer.
However, with all that being said, summer PHL-PMI is one of my "wild card" picks for AA. PMI has an extremely strong European pull, and it's not inconceivable that it could have some pull from the US too. DL runs JFK-AGP in the summer and seems to be doing fine at the moment, and PMI is significantly larger than AGP (AGP had 16 million pax in 2016 while PMI had 26 million pax). PHL also has a better domestic feed than JFK does, and PMI would have a decent OneWorld pull from IB and BA, so AA would have codeshare partners if they needed it. So a little off topic, but my bold prediction is that AA will eventually launch a summer seasonal PHL-PMI with most likely the A321neo. May still be a few years out, but my bet is that it may happen within the next 3-5 years.