Are whole-house GFCIs legal in the US?
The protections do totally different things

Seriously, you do not understand the purpose of RCDs in Europe. All our attempts to make electricity safer are based on compromises between what is possible and what is affordable/implementable. These are greatly swayed by accident data which tells what kinds of accidents actually happen there. Which in turn reflects on housing stock and culture.


Parallel arc-fault protection is about arcing faults between Hot-Neutral, Hot-Ground or Neutral-Ground, which make heat. 
Series arc-fault protection is about arcing faults inside an intended connection on a hot or neutral wire, which make heat.  
Ground fault protection is about wayward (residual) current returning through some alternate current path, e.g. a human.   


Europe's goal is to as cheaply as possible provide parallel arc-fault protection...  while providing some very limited degree of personnel anti-shock protection. 

America's goal is to protect human lives from electrical shock where small-appliance receptacle outlets are near water.  Arc fault protection doesn't even enter into it.  GFCIs are usually in the wrong location to provide any sort of effective arc-fault protection; but they provide excellent parallel H-G and N-G protection (and none at all for H-N).  Arc-fault will come later as a separate initiative. 

Let's try it Europe's way

You can put American, human rated GFCI on a whole-house if you really want to.  Easy enough; just get a 60A GCCI spa subpanel and power a larger subpanel from that. 60A@240V is large enough for every load in an American house except the fixed 240V ones like water heater, A/C, EVSE, range, electric dryer, etc.  Spa panels are about the price of a 2-pole GFCI breaker, so you won. Congrats.

snap

Wow, all your lights went out.  What happened?  

Well, you know those six smart switches you insisted on installing on your old switch loops, where they had separate green and bare wires, and the instructions said put the green on neutral if you have it, otherwise put it on ground?  Each of those returns 0.5 ma on ground.  Your bathroom fan, that has a 0.4 ma leak to ground. Your cheap PC power supply has a 0.9 ma leak. The coffee maker, 0.4 ma. The fridge, 1.5 ma.  

"But wait.  I have these exact same appliances in Chateau TooTea in France.  Why don't they trip the RCD there???"   

Since US breakers are focused on human safety, they trip at 5 milliamps.   Europe only is after parallel arc faults, so they threshold at 30 milliamps, precisely so these numerous micro-faults do not "stack" to cause the RCD to constantly nuisance-trip.  30ma gives enough headroom that such trips aren't a problem.  The downside is it sucks at human safety. 

"But they're spread out! There isn't more than 2ma on any one------ Oh... right. Curse my whole-house GFCI!"

... And that's why Americans use per-circuit GFCIs.  It allows our detection threshold to be low enough to protect humans. 

Alright, lesson learned, let's try a 30ma whole-house

Yeah, that would actually work, but it would work in the European way, being a watch dog for H-G and N-G arc faults in in-house wiring.  

Now one problem in American homes is that you have a few very large appliances that don't really benefit from GFCI or AFCI if they're grounded - range, A/C, water heater, dryer, EVSE, electric emergency heat on heat pumps, etc. If you recall before, I excluded them from the 60A GFCI panel because they're too big - they'd gobble up the GFCI capacity without benefiting from it. So I'd recommend doing the exact same thing here. 

OK, what did this buy you?   


Very weak GFCI protection on the circuits that don't already have it
Parallel H-G and N-G arc fault protection
No H-N parallel arc fault protection
No series arc fault protection.


For a grandfathered house that will not have per-circuit Combination AFCI protection anytime soon, would that be an improvement?  Sure.

For a modern house with 2017 tier GFCI+AFCI protection, probably a complete waste. 

Dat wascally wefwigewatah


  One could also say that it's safer, because it forces people to actually fix the fridge that trips the GFCI instead of removing the GFCI.


How is it safer exactly? What a silly thing to worry about.  

Mind you, you must consider perspective: Americans are after human safety, where GFCI'ing a grounded fridge accomplishes nothing.  In the European perspective, it reduces fires caused by >30ma parallel arc faults on the wiring to the fridge, or inside the fridge.  Which is a thing that could actually happen.  And, the ordinary fridge ground faults that vex Americans are almost never over 30ma.  So they would never trip a European home at all. 

Keep in mind, when you hear about fridges tripping GFCIs, the fridge may not be faulting at 5ma.  It may be on the same circuit with that coffee grinder, those two smart switches, etc. which all stack to 5ma.


  The main advantage of this solution (apart from being cheaper) is that it's trivial to retrofit to older houses without having to disentangle all the neutrals first.


They're not supposed to be entangled in the first place.   And one thing you'll hear me say a lot (to newbs) about GFCI receps is "Stop using LOAD. Seriously. For wizards only."  And the reason I say that is so novices can avoid issues with the downline, such as ground-faulting hardwired appliances and crossed neutrals that the novice is really not prepared to fix.  It would be marvelous if everything got fixed 100%, but that is not going to happen. 

Also the vast majority of so-called "entanglements" are actually intentional multi-wire branch circuits.  Those are fine. They need 2-pole AFCI (in most cases) and either 2-pole GFCI or per-receptacle GFCI.