They tell all the Canadian banks and financial institutions that they have to ask all customers whether they are US citizens (and you lose account access if you won't answer).
The Canadian banks then have to report all the accounts of US citizens to the US gov. The banks comply with all this because otherwise they get super nasty fines against their us operations.
Also: they tell you that if you come in under the amnesty program (like I did) that their will be no big penalties - but if you wait until the amnesty program expires - and they then find you - they will treat you like a criminal.
The Canadian banks then have to report all the accounts of US citizens to the US gov. The banks comply with all this because otherwise they get super nasty fines against their us operations.
Also: they tell you that if you come in under the amnesty program (like I did) that their will be no big penalties - but if you wait until the amnesty program expires - and they then find you - they will treat you like a criminal.