The number of backlogs allowed in an undergraduate program to get an MS in the USA depends on the specific university and program that you are applying to. In general, universities in the USA do not have a specific limit on the number of backlogs allowed, but they do consider your academic record as part of the admissions process. When applying to an MS program, universities will typically require you to submit transcripts from all the colleges and universities you attended, as well as other application materials such as letters of recommendation and a statement of purpose. The admissions committee will review your application holistically, taking into account your academic record, test scores, work experience, and other factors. Having a high number of backlogs may be a concern for some universities, as it may indicate that you have not been able to keep up with your coursework or may not be fully prepared for graduate-level study. However, if you can demonstrate strong academic performance in other areas, such as your test scores or previous coursework in your major field of study, you may still be considered for admission. It is important to research the specific admissions requirements and policies of the universities and programs you are interested in, as these can vary significantly. You may also want to reach out to the admissions offices or faculty members at these universities to ask specific questions about their policies and how they evaluate applicants with backlogs.