I am not studying in Romania, but I am across the Danube in Bulgaria... I may be able to add some additional clarifying information.
One of my goal would be to practice medicine in the usa (Californiaaaa ). Before, I'm thinking about following the medical studies at Oradea :
Unfortunately, this would be impossible if you study at an English-language program in Romania. None of the English programs in Romania (or Bulgaria, or Serbia, etc.) are approved by the California Medical Board. ONLY the Romanian-language programs are approved, and believe me, the CMB knows the difference. The only English-language programs in Europe that are CMB-approved are found in the UK (obviously), Poland, Czech Republic, and Hungary... and not every English program in the latter three countries is approved. I believe that every native-language program (French schools in France, German schools in Germany, Austria, Switzerland, etc.) is CMB approved.
Is the usmle difficult to obtain when you study at the university of Oradea and how is it going (in wich year do you start the first steps etc...)?
In general, if you are studying in E-Eu, you will have covered the necessary materials for USMLE Step One by the 4th year of study. However, as waltfw pointed out, there are distinct differences in presentation here, so it is not an easy undertaking. The USMLE is a challenging exam, especially for those who do not have English as their native language.
What is the exact specialization to be an emergency room doctor in the USA and how many time of residency does it take ?
Emergency Medicine in the USA is a three year (or, in some academic centers, four year) residency after graduation from medical school. It is quite competitive right now, and not easy for foreign medical graduates to be matched into a position. You need high scores on the USMLE Step One and Step Two CK, as well as a passing score on the Step Two CS (which is only offered in the US), and you need these passing scores to be on the first attempt. Even this is no guarantee, however, as you will also need letters of recommendation from EM physicians in the US, which you can only receive by doing a clinical elective there during a vacation period.
_Do you think that by following my studies in Romania, I could easily become an intern and then an emergency room doctor (or any other specialization) in the USA or would it be very difficult because of the way that recognizition of diplomas work and because of my european nationality (visa...)?
No. It is not easy to become a physician in the USA, especially in Emergency Medicine. Recognition of the diploma from Romania is only one challenge (because it is not recognized in California and about 10 other states). You would also need to convince a residency program to provide you with a training visa, which costs them a lot of money and effort, unless you have a green card or US citizenship. It is far more likely for a foreign graduate to match into Family Medicine, Pediatrics, Internal Medicine, or Psychiatry, and even that is not exactly a piece of cake.
_ Do you know some students who, after their 6 years at oradea, did not find any interessant residency outside Romania (they wanted to go in ireland, uk or usa and they did not get it, they were obliged to pursue in romania to obtain their spe)?
There are literally thousands of foreign medical graduates who do not match into a residency in the US every year. This is not specific to Romania, these unmatched physicians come from all over the world.
I hope that helps, and I am honestly not trying to rain on your parade. It's just the way things are... even those of us who are US citizens studying abroad are finding it harder and harder to match in the USA. There are a lot of new medical schools opening in the USA right now, and these students will always get matched into a residency before someone who graduated overseas.
"To array a man's will against his sickness is the supreme art of medicine."
- Henry Ward Beecher