It really is quite a big stretch to assume that this is a causal mechanism. You only need to look to Scandinavia to find a counter-example.
I think it is more reasonable to argue that high salaries in US are fuelled by borderline slave wages for menial labour. And Switzerland's wealth comes in a historical context that is completely different from the US - it's almost impossible to blanket compare them side-by-side. The difference in population size is another huge issue with such a comparison.
So effectively, the burden of proof is on the employer to show that the reason for firing is a legal one, but that does include "orders drying up so we need to cut back on staff who would otherwise be idling".
Courts can and do award fired employees up to 6 months' salary as compensation if employers overstep the lines here. And because Switzerland has a well-working legal system, that means most employers don't abuse their firing powers, and making a facebook post on $CULTURE_WAR_TOPIC from a non-work account is unlikely to get you fired unless your role is "brand ambassador" or executive officer, for example.
Also, if you are fired in Switzerland and you're a citizen, you have very generous (by international standards) state redundancy/unemployment benefits.
I agree with the parent poster that the flexible labour laws are part of what makes Switzerland attractive for business, but I would much, much rather end up being fired under the Swiss system than the U.S. one.
* rupture conventionnelle, by mutual agreement, which requires at least 1/4 month salary per year on the job for less than 10 years, 1/3 month for more than 10
* licenciement économique, which has a mandatory procedure, and requires 1-2 months notice of the employee, with a compensation same as the above
Since the procedure for the second one is a bit involved and requires approval from the mini-union embedded in all companies over 50 employees and a government agency (since it's only intended when there's economic troubles), often employers would prefer to pay extra compensation in a rupture conventionnelle instead of wasting time with the procedure.
Honestly doesn't sound much more complicated than Switzerland, yet nobody would say this allows France to have low unemployment.
Post hoc ergo propter hoc. There are plenty of other reasons that the US and Switzerland have become wealthy, you can't simply assume that liberal labour laws are a factor.
Any form of this comes from abusing the temporary work and contractor system(not exclusive to Eastern Europe, but here it's common).
But still - even as a pretend temp worker you normally don't get fired on the spot without notice because with the current demographic situation employers can't afford to do this and will usually include some form of notice in the contract to protect their interests.
Also illegal employment, especially in construction, is still very much a thing around here and I would think that, if anything, is a greater factor.
Easier to get ahead when you're cheating.