Why is OKX not working in the USA?

Could you please clarify why OKX, a renowned cryptocurrency exchange platform, is currently inaccessible in the United States? Is it due to regulatory restrictions imposed by the relevant authorities in the country? Or could it be an operational decision made by the platform itself? Are there any alternative options for cryptocurrency trading available for US-based users? Understanding the underlying reasons behind this situation would greatly help in navigating the cryptocurrency landscape for those residing in the USA.