I wouldn't worry at all, no idea if this crap is still technically required or not, but in any event they can take any necessary info at the airport.

On my last trip to the US in June I got the same email from AA, also clicked on the link and also got sent to a blank page. Didn't think anything else of it. When I got to the BA check-in desk (flying AGP-LHR-RDU) the agent asked me to write down my address on a piece of paper and proceeded to check me in with no issue. No clue whether she actually entered my address into any system or if it was just a formality.