Firstly, I'd like to preface my comments with a link to http://www.sloperama.com/advice.html
which is where I have gleamed most of my own "advice". Its a great site, and full of specific practical advice to consider.
Couple of points:
1. Do you have a right to work in the USA (VISA/Green Card/Citizenship)? If not, then you might be stiff out of luck there and best to focus on Canada/UK/Ausi/NZ. The USA only makes a certain amount of VISAs available for this category, and last year they all went on the day they were released! To get a company to sponsor you, they would REALLY need to want you. So you'd need alot of experience.
2. Review the Gamasutra website for jobs that you'd like. Check to see what their job requirements are, and then ask yourself if you portfolio etc... proves how you have every single one of those points.
3. Follow http://www.sloperama.com/advice/jobapp.htm
for advice on how to apply for jobs. I recommend that once you have a good resume and portfolio, that you approach companies rather than waiting for advertisements.
4. Specifically, I think the portfolio needs a bit more detail about what role you took in each example, what the example was used for, etc...