It's about illegal immigration, there is a difference.
All Bush has to do is talk about the US and what he plans to do for the citizens of this country. How many Americans do you think want to hear about the problems of foreign countries and the nice things we're going to do for their illegal citizens in ours? I'll bet it's not many.
As far as the best interests of the country: that often comes down to what the voters think those best interests are. Grey Davis just found that out in California, Bush 1 and Carter learned it the hard way too.
It doesn't matter anymore. It's party over country, it's party over law, it's party over the constitution.