I am applying for some (second) master programs and a few Ph.D. programs. I earned my undergraduate degree outside the US but got my master degree in an American university (I am an international student). I wonder if I can only submit the transcript of my first master degree for my application?
The general answer to this question is no, your undergraduate transcript is required as well.
The reason is that for master's degree programs where coursework dominates, undergraduate success is usually a good predictor of graduate success. While for PhD admissions, they don't have as much predictive value (since PhDs are about research, not classwork), it is still important to have a baseline for judgment.
In addition, the schools will want to check if you have the necessary prerequisites to undertake PhD studies. This usually requires your undergraduate transcript.