I fantasize about doing that sometimes, but usually, you can't get into politics without being a citizen — either due to legislation or because you won't be accepted as a representative by the population, for obvious reasons.

But assuming you can get into politics, you'll still have to deal with an enormous struggle for power (be it elections you have to win or powerful people you have to convince) in order to get into a position to even make any change.

Thus, this endeavour is practically impossible — it's already difficult enough to change something in your fatherland.

AFTER tokenadult's EDIT: Your edit clarifies a lot. But fraternalism is still difficult to achieve: if you are from a different race than the native population, you'll have a hard time being accepted as their representative.

An interesting example for this might be Singapore, where Lee Kuan Yew pushed the country from third to first world in 50 years. Although he is Singaporean, he brought in a lot of foreign knowledge as he had studied abroad. And the same issues with corruption/illegal methods some commenters mention here can be observed: in the early days of his career, he arrested his opponents, the communists, without any legal process to prevent them from jeopardizing his plans. Later, he made some radical decisions, that were not widely accepted by the population, bu that led to better results for the country (for example, he tore down old villages to replace them by high-rise buildings).