Lately, my wife's been doing now international travel than I have, and she reports that foreign airport security for flights to the US are far more strict than domestic flights. For example, TSA in the US is pretty loosey-goosey about the liquids rules - not the amounts, but having everything in ziplock bags that can be closed. I haven't put my liquids in ziplocks for a domestic flight in years, but foreign security enforcing the TSA checks are anal-retentive about stuff like that.

Part may be because we've had pre-check since it first came out, so I may just be seeing only the less strict rules of pre-check, but I suspect the US is just more strict with airport security for incoming, non-domestic flights, and foreign airports are just doing what TSA is demanding, to the letter.

Heathrow, Charles de Gaulle, and MUC's security are way more lax than any US airport. Where they get strict is when you get to the gates for the US flights and have to go through security - TSA, this time - a second time. The only airport I thought had general security as strict as a US airport was Singapore, and their TSA at-gate security is insane. Dubai, too. Only airport I've been in where the entire gate for a flight was enclosed in glass, like a snake terrarium. And god forbid you wanted to go back out for food or something, because you had to go through that TSA checkpoint again. I hate flying through Dubai to get home.