As I look back over the past 25 years, I just can’t–for the life of me–figure out when it became conservative to be anti-immigrant.
Reagan spoiled me as a kid–with his many (sincere) apologies to Japanese Americans for their internment in WWII and his apologies to American Indians. And, his praise of those who came to America to work hard.
I always identified the Republican party with pro-immigration and pro-labor. The Democrats–with their support of labor UNIONS–were the anti-immigrant folks.
What happened? I ask this in all sincerity.
To me, conservatism will always mean relatively open borders–free movements of peoples–whatever the anti-immigrant folks say today. That is, it should be closed to criminals and terrorists but open to anyone who is trying to improve his or her life.
Granted, I’m proudly neither a member of the Republican Party nor the Democratic Party. Each is fundamentally corrupt.
Stormfields 
Conservatives have always been opposed to invasion by a hostile power. Tom West has some of the best stuff on this subject.