They're largely not enforceable in the US either - non-competes are thrown out in court all the time.
Enforceability is only one (small) dimension of the problem - arguably the chilling effect it has on future employers (who simply don't want the show up in court, even if they will win) is larger.
The threat of litigation is often stronger than the litigation itself, especially against smaller entities. Overly broad non-competes are more a bullying tactic than they are an actual contract.
In 45+ states some form of non-compete is legal. Other than CA, most big states allow it. Most non-compete clauses in practice are probably unenforceable (because they are too long, cover too large an area, covers too big of a market, etc). But I'd be pretty worried about one if I wasn't in California, and I'd never except it.
Enforceability is only one (small) dimension of the problem - arguably the chilling effect it has on future employers (who simply don't want the show up in court, even if they will win) is larger.
The threat of litigation is often stronger than the litigation itself, especially against smaller entities. Overly broad non-competes are more a bullying tactic than they are an actual contract.