Only importing immigrants who have political views that agree with yours? A country has a particular culture and set of views. Why would we want to import people from countries with inferior living conditions and follow the way they do things? There's a reason they left.
As for why let people in from poor countries, because we are siphoning off the most educated and ambitions people from that country, who bring their drive and good genes to our country. It's the same reason Asians, who consist of the top people in their home countries who chose to came here, do better in the US than blacks, who were brought here by slavers.
What part of the point "let people in from poor countries, but don't let them keep doing things the way they were doing them" is not clear? Sure they want to move here, don't let them turn this place into the place they left by making them learn the language and culture.
>It's the same reason Asians, who consist of the top people in their home countries who chose to came here
That is an incorrect statement. Most asians who first came to america were imported as cheap labor to compete against Irish unskilled labor. The Polish, Irish, and Italian who came to the states were definitely not the best and brightest, but because they assimilated and learned the culture prospered.
Relying on other nations is the exact opposite of national security and it's naive to think that they will be by our side when shit hits the fan. We've seen too much in the last hundred years to leave our most critical industries to chance.