The tolerance for backlogs in an undergraduate program when pursuing an MS in the USA can vary depending on universities and programs. Generally, having a limited number of backlogs (1-2) might not be a significant hindrance, but a strong academic record is preferred. Admissions committees consider various factors beyond backlogs, such as GRE/GMAT scores, letters of recommendation, and statement of purpose. It's advisable to research specific program requirements and focus on overall academic excellence for a competitive application.