Calgary customs at 11am can be a very busy place. Leaving within 2 hours of 11am security time arew the following flights: ORDx2, DENX2, IAHx2, LAX, JFK, SEA, and SFO. The UA and AC counters are very busy at this time of day.
See the above poster for cnx bagage information. There is a USA connection signage directing traffic, the signs are located about 1/2 down the checkin line. Unfortunately the pathway is sometimes not clear as pax in check-in lineup sometime block the path way.
US Customs officers are busy at this time of day and 15 minute line-ups are not unheard of. Last year at this time the security line-up was a conx killer. It can take up to 30 minutes to clear the security area. HOWEVER CATSA has improved considerably since January with a huge increase in staff. Therefore I do expect to make the cnx.
Of course there is the unforseen problem of stopping short of the gate, which is very common for AC operations at YYC. This could delay things by a few minutes.
55 minutes is tight but doable so long as the BP for YYC-USA portion is retreived at origin.