You have a lot of questions that we can't give all the answers. If you want to choose a specific U.S. State, google each State. There are 50 States and other territories like Guam, American Samoa, U.S. Virgin Islands and Northern Mariana Islands. USA is such a big country. You also mentioned California. Well, I live in California, and it also depends on where you live here.
My suggestion is for you to look for an agency that will help you understand the process of getting here. You cannot work in any of the State here without passing NCLEX-RN, so your agency will help you process that, just like what @SpidersWeb enumerated on the list. Each U.S. State has a different way of processing an application especially for an IEN (internationally educated nurse) like you. Since you're still there in the Philippines, you might choose a State that doesn't require SSN (social security number) because most of the States require that. Again, your agency will explain it to you, and I guess different agencies have different amount of expenses too. So choose wisely.
You mentioned disadvantages and advantages. I guess there are more advantages living here. You get paid well, and you can sustain your needs despite of cutting your monthly income from your monthly bills. May I remind you also that USA is a country of bills. You will know that more when you get here. Especially when you become a driver with your own car, you will pay for your monthly car insurance and monthly payment for your car if it's leased, or financed by a dealership. We have buses here but as a nurse, I don't think so if commuting a bus is appropriate (not to degrade or negate riding a bus, but you have to wake up early and you have to be in your workplace on time). You need a car. If not, you need a person who will give you a ride.
I'm sure, by the time you have passed NCLEX-RN, and have gotten your working visa, your agency will orient you about travel, expenses living here, bills, transportation, people here, and so much more especially for the State where you want to settle down. So look for an agency that will help you achieve your goal to migrate over here. And don't forget to post about your success stories here at allnurses. GOOD LUCK!