Yes, we could. The people that are dismissing border security and saying it cannot be done would be singing an entirely different tune over this invasion if it was happening under a Dem president.
IMHO, the invasion has already happened. Casloy's scenario is very likely to have already happened and closing the borders now, even to TMcG's 95% would be closing the barn door after the fact. If we're getting information that the government has supposedly had since August about 25 Chechens entering the US, you can bet that they've been doing it for years in groups of one's and two's. Why they would even risk a group of 25 is a good question. How many of the 9/11 terrorists were in this country ilegally? At a 95% border closure, what would be the international reaction? I'd bet that any country we closed our borders to, would close theirs to us. That's a great way to escalate a war on terrorist factions to a world war.
The only reason they are saying this is because they're candidate/candidates have done little or nothing to stop this epic coast to coast lawlessness.
As a matter of fact, they're candidates more then likely are aiding and abetting and pandering to this lawlessness, and have absolutely no desire to end it. Like the greedy employers that hire these criminals, as they sit in their back offices counting their profits on the backs of the tax payers. They too have no desire to reduce their profits.