There are two hard conditions for doctoral studies in the United States: on the one hand, the academic qualifications and academic requirements for doctoral studies in the United States, and all students with bachelor's and master's degrees can apply for doctoral degrees in American universities. If the undergraduate directly applies for a doctorate, the requirements for the applicant will be more stringent. Applicants must have sufficient research experience and background and outstanding performance in the professional field, and have completed many courses at the master's stage, which is what we usually call equivalent academic ability. Similarly, applying for a doctorate from a master's degree also requires research experience and professional writings.
On the other hand, it is the language requirement for studying in the United States, which is a necessary condition for studying in the United States. The minimum language requirement for doctoral applicants in most universities in the United States is that TOEFL is not less than 550 (new TOEFL 80). Applicants for doctoral degrees must produce GRE or GMAT scores, and the quality of the scores accounts for a considerable proportion in the application. Some universities have strict regulations on GRE or GMAT scores of doctoral applicants.