For example, consider Bob and Fred. Bob is good at hunting, but stinks at growing blueberries. Fred grows luscious blueberries, but he's likely to blow his own foot off when hunting.
Bob brings home twice the meat he needs, and Fred grows twice the blueberries he needs, and they trade.
They are both better off than if Bob and Fred each only fended for themselves.
BTW, back in the 80s, my (British) partner at Zortech noticed that boxed software in Britain sold for twice as much as the same box in the US. So he would order large quantities of boxes from the US, mark them up, and sell them locally at a nice profit.
Eventually, other businessmen caught on and this no longer worked.
That's arbitrage in action. It benefits consumers.
On the short term and reasonable spatial scale; sure. What's currently happening in the West is that common people are discovering that on the long term and at world scale, it does not really benefits them for a myriad of reasons, among which unevenly applied norms, difference in regimes, different social models, etc.
It's not really about building a wall around your country to keep people from fleeing, but to prevent gadgets sold by people leveraging arbitrage in an unfair way to get in – or, as we call them for now millenia, tariffs.