First, I assumed you were a Filipino citizen because you posted in the Philippine forum. Second, you didn't mention that you wanted to focus on critical care for your master's degree so I also assumed you were undecided on what route or specialization to pursue. Third, you also did not mention that you already have experience as a nurse.
Taking all that into consideration, I think it is not such a bad idea for you to pursue a master's degree in the US if you can come up with the funds to support your application for a student visa, your tuition, and cost of living allowance once you arrive in the US. So, let's assume that you are able to finance your education if that's OK.
The first step for you is to figure out where you will study. There are "prestigious" universities in practically every major metro area in every state of the union. However, cost of living varies depending on where you are in the US. The southwest coast (for instance, Southern California and even Northern California) is very expensive and so is the northeast (cities like New York, NY and Boston, MA).
These areas definitely have one of the best schools for a master's degree in nursing. But do not overlook the middle states. There are also excellent programs in universities in the midwest, the south, and southeastern areas of the US. The advantage in going to school in those states is that the cost of living is usually more affordable.
I suggest you find a program you like by doing your own research. In order to specialize in critical care, you have the option of attending a Clinical Nurse Specialist program with a critical care nursing concentration. There are also Nurse Practitioner programs in critical care. If there are NP's in your home country, this can also be an option for you.
Once you find a program in a university and a city you think you might be able to afford, then the next step is to apply for admission to the program. Most universities will send out application packets in the mail even for overseas student applicants. They will also help you along the process of obtaining a student visa.
Good luck to you and if you have any further questions, don't hesitate to ask or repost.
Forgot to mention too that for clinical-focused master's degree programs in nursing (i.e., NP, CNS, CNM, CRNA), a US RN License is required. Some programs may allow you to register for non-clinical courses (i.e., theory courses, medical science courses) even without a US RN License, however, you would need one prior to starting any of the clinical courses. GRE used to be required across the board but I'm seeing some trend in certain programs where this requirement is no longer specified.