If they were going to speak, it MUST be in the language of the patient, which in the USA has to be English.
The US has no official language. Other countries like Belgium have official languages, but this pertains only to interacting with official administrations, ministries, public servants, police, postal workers etc. Otherwise people may speak whatever language they wish among themselves.
The US, having no official language at all, is thus even more in this situation. People are free to speak whatever they wish. It has probably been decided in one or another of the never-ending Supreme Court decisions somewhere along the line of history.
Besides, the US has some 63 million non-English speakers. That is around 20% of the population. More than Belgium has for instance. And being in the EU, we have workers, nurses too obviously, from many countries, Poland and Romania being especially represented. They are given training in Dutch of course for patient interaction, though most are better versed in English.
But if they wish to talk to a colleague in Polish or Arabic even or whatever, it's their choice. Whatever promotes the least misunderstandings. And honestly no one cares, as long as the treatments are up to standards.