Actually i was unimpressed by these test pilots in the youtube clips, since they made no effort to decrab at the flare.
The 737 is limited to 19 knots crosswind with minimal flaps and 23 knot crosswinds with 40 degrees flap. The limit applies to aircraft which are not de-crabbed. The limit is set not by the aerodynamic limit of the aircraft but rather by the strength of the undercarriage to resist hitting the runway sideways.
If the aircraft is de-crabbed to align with the runway in the flare then the risk is removed and theoretically if you use proper technique there is no limit.
I landed a Gulfstream Cheetah at Wellington's runway 16 in 45 knot winds gusting 55 knots from 240 degrees once. The crosswind limit on a Cheetah was 11 knots, but if you land properly it will handle that. The limit is on the undercarriage strength and not aerodynamic factors.
Wellington is a wind factory and it is not uncommon for Air NZ B733s to land with 50-60 knot crosswinds. Course the passengers often don't appreciate it.
Oh and PS: The rudder is used to equalise the drift. the aileron to slip towards or away from the runway as a form of minor adjustment to track the centreline. Always de-crab before touchdown, by kicking the ruder to point along the centreline.