The illusion is a patrolled border. For purely political reasons, it is porous as a sieve. The human smuggling is bad enough, but contraband is also getting through. On that point the Republicans have a completely legitimate gripe.
So, now it's a fully partisan position? There's an idea that the Democrat administration pisses Border Security budget money away and don't strive to spend it in an efficient way to stop migration through the border?
That's laughable. The border will always be porous, you can reduce the flow using an exponential increase in spending. It's the nature of such things. So, the question is more 'how much money do you want to spend?'. The idea that one administration could be vastly better at this task is a pipedream, given equal budgets.