Habilitation is not a term in common use in the US, but if the Wikipedia article is accurate about the meaning, then it would seem that a holder, with no other qualification, would likely be eligible for a faculty position at one of the lower ranks: Assistant Professor or Associate Professor, perhaps.
Most full professors only get there through promotion, not directly. Sometimes an associate professor will be hired as full professor if they are at the verge of promotion at the first university. And a few (very few) people might be hired directly at full if they come from outside academia with an exceptional research record. But in such cases the person can expect to have a short probationary period. So, with habilitation (and a PhD) in hand, more is needed to be hired at full rank. And without experience in academia other than as a student, even initial hiring at associate level is not assured.
But if the person had other relevant experience and held a position similar to full professor or associate, then they might be considered for full professor.
But the holding of it, alone, wouldn't likely be enough. It would further depend on the work done by the person, perhaps the same work that led to the awarding originally.
So, with respect to the final paragraph, most would consider the holder to be very proficient, especially in the German or Austrian case. But every holder of a doctoral degree would be considered very proficient, also. I have no way to guess whether the situation in Poland is the same.
If you hold a PhD or equivalent then habilitation probably doesn't mean much in the US. If you don't have a terminal degree and want to use habilitation to get employed, then you will need to explain in detail what it means in the country in which you earned it. For those jobs requiring a doctorate it might be hard to convince them depending on how firm the rules are. But don't expect that it will be automatically understood.