Plays both ways. As many British kids denied low barrier entry to Europe suffer as people who saw their job value defended. And, cheap EU/shengen labour was just replaced by non EU equivalents, driving the British right wing faragists even crazier. It also dis-incented the French to stop migration transit across the channel in boats. So, Labour cost dilution happened anyway. And small business tanked with market access losses.

All of this could affect the USA. Sales of US sw and service, access to European CDN and DC markets could dry up, and startup culture see less interest in product in the wider market, as H1B displaced workers "back home" carry American models into their domestic VC market.

Tbh, I think that's less likely to work. People (not me I hasten to add, I'm past the age) want to move to an idea of America they grow up with, and VC friendly economics don't export well: people outside America hate failure.

I guess I'm saying current WH policy doesn't favour the "open market" side of this, regarding non US market access and there will be a consequent reaction in those non US markets to American labour and ideas.