If Bush thinks we can eradicate insurgents from Iraq, then why can't we deport illegals from America???

Answer 1

Bush incorrectly thinks that military operations can end a civilian insurgency, but it can't. His mistakes have no bearing on the issue of illegal workers.

Illegal workers in America can't be rounded up and deported because they are performing work vital to our economy and we are not prepared to replace them. This fact is politically unpopular, but it is still true.
A military operation on American soil to catch undocumented aliens and deport them is also illegal, so that can't be used even if we were prepared for the vacuum that their removal would cause.

Answer 2

I think the Mexican government has threatened the US. They want us to keep the border open, income from the US to families in Mexico is the third largest source of money in Mexico. The largest sorce of income in Mexico is oil. They sell most of their oil to the US. Hmm . . . If the border is closed Mexico loses money, and could choose to sell their oil to China.