Constructive dismissal laws vary by state- but generally, if the compensation and job duties remain substantially the same, it won't be constructive dismissal in the US. The post alludes to the possibility that the new company will make changes after 6 months... if they substantially reduce compensation at that time or substantially change the nature of the job, their us employees would probably qualify for unemployment.

Notably, the Reddit poster is from France, so this sin't a "US vs Europe" thing as some other comentors are trying to make it out.

Also, looking at https://www.iamexpat.de/expat-info/social-security/unemploym..., seems unemployment in Germany is similiar, but in some situations less than in the US- though it can also, in some situations, last longer.

That is not legal in Germany, because that requires a new contract, which you can refuse to accept and have to be compensated for.

Meaning, it does happen, but it requires the workers and union to accept it actually takes place, the company cannot just decide on their own that they will do it and that is it.