Having joined the party fairly late, I thought I'd have a go at explain how the FBW works in a crosswind. Here goes.....
The airbus is an aeroplane, just like any other. In any other aircraft, as you decrab during the flare, you must apply into wind aileron, which gives a sideslip (!) and the net result, if performed correctly, is that the aircraft aligns with the runway, and is banked slightly into wind so that you do not drift off the centreline.
Sideslip requires a bank angle to maintain the track - hopefully runway centreline!
As the crosswind (and hence crab angle) increases, then the amount of rudder and aileron (and hence bank angle) required increases. Airbus says
"In the case of a very strong crosswind, the aircraft may be landed with a residual drift / crab angle (maximum 5°) to prevent an excessive bank (maximum 5°). Consequently, combination of the partial decrab and wing down techniques may be required. "
So, how does this fit in with the world of FBW?
After 0.5 secs airborne, you go into Normal Law, and stay there until touchdown. In roll, you demand a roll rate. Stick input results in a roll demand, until you get to the bank angle you want, when you reduce stick input to zero. Aircraft stay in bank angle selected.
During landing to remove the drift, we input rudder. To keep the aircraft on the centreline, you need some bank - the sideslip as described above. However, in my airbus experience, if you boot the drift off quickly, the control law is slower to respond and it will not catch the roll quickly enough. If you're more gentle - e.g as a previous post gave the example of sideslipping when downwind on base training, - it will keep the wings as you previously demanded i.e. level.
However, you don't actually want level, as you need some bank angle to keep it on the centreline. So you need to demand a small bank angle - using stick input- then take out the stick input when you get to the angle you need.
That's the tricky part!
For people like myself, , taking the stick input back out goes against all the muscle memory we've acquire on previous types. So you need time to get used to it.
For small crosswinds, we don't really bother too much with extra stick inputs, as the decrab and subsequent bank required is small. However, in large crosswinds, as the drift is taken off with the rudder, bank is required to maintain the centreline. And be aware what airbus say about large crosswinds - they don't want more than 5 deg bank angle, so they're happy if you land with some drift.
In summary, great piece of kit, but we all fight against our experience on previous types when we start to fly it. With crosswind landings, I still find myself putting roll rate demand in, but forget to take it out again!