Is Nexo allowed in US?

Could you please clarify for me if Nexo is permitted to operate within the United States? I've heard about its services but am uncertain about its legal standing in the country. Is there any specific regulation or license that Nexo needs to comply with in order to be operational in the US? Additionally, are there any restrictions or limitations for US citizens using Nexo's platform? It would be helpful if you could provide some insight into this matter. Thank you in advance for your assistance.