In security parlance, you do both 'upstream' and 'downstream' checks on anyone crossing borders. Be assured, nobody who has bought an air ticket and filled one of those Esta forms has not had an 'upstream' check: this will be against your 'control file' held by the NSA and populated with data from multiple sources, including Canada's CSIC (Canada has had its databases merged with the US since at least the early 1990s). The phone fiddling and body pat downs are nothing but Kabuki theatre since they already know if you are a threat or not. 

If you are crossing into the US, remove any excuse they may have to hassle you: go clean. No digital devices, dress smartly, take little in the way of baggage apart from your clothing for a week, if you have a laptop, upload everything into the cloud so it is also clean.