Permanent versus temporary admission
There are a lot of ways that you can be admitted to the United States. Most are temporary but this may still be an option that is worth looking into if you are finding that it is difficult to get a green card. In some cases temporary admission can last for years.
The goal of most people who are looking to move the US is to be able to stay there permanently. Most want to start a new life there and eventually to become citizens. This however creates a bit of a problems since there are far more people who want to move to the US than the country can accommodate. The result is that it is very difficult to get the green card that allows you to move to the US. This is why a lot of people have to settle for temporary admission.
The best chance that you will have of being able to get a green card will be if you have a close relative living in the US. Far and away the most green cards are issued for family reasons. Therefore you have a distinct advantage at gaining permanent status if you have a relative in the US already. The other option that may work is if you can get a green card through employment. This is much harder to do and most people who want to work in the US find that it is much easier to get a temporary visa.
Temporary work visas are a lot easier to get than a green card is so this may be an option that allows you to move to the US. These visas can allow you to stay for anywhere from a few months to several years. There are a lot of other visas that will allow you admission to the US but these do not allow you to work. If you are planning to hold a job in the US you will have to get a work visa. In general the best chance of getting one is if you are highly skilled in a job that is in high demand. Alternatively you may be able to get one if you want to do a menial job that few Americans are interested in doing. The jobs that fall in between are much harder to get visas for.
One thing that a lot of people wonder about is whether a temporary visa can help you to get a green card. The answer is sort of. You cannot get a green card based on a temporary visa. However the criteria to get one includes things like how well you will fit in and how likely you are to get a job. Having lived and worked in the US on a temporary visa will give you a chance to prove that you can do these things. This may help you if you decide to apply for a green card down the road.