In principle you can be “interviewed” for any length of time at the point of entry. Granted, the immigration officers don’t necessarily want to waste their time and resources, but I’ve been questioned by immigration officers at times when I had to rush to connections because of late arrival, and it certainly felt like the questioning was quite time-consuming.
If you start from a pre-cleared airport, then all of this will happen before you can even get to the boarding area. As far as I can see, the only Canadian airports with flights to DFW are Toronto (Pearson), Montreal and Vancouver, all of which are pre-clearance points of origin. Thus you will arrive at domestic gates without further immigration or other checks, as if you were arriving from a US point of origin. There is a wiki page providing a list of airports with pre-clearance.
The situation will likely be different upon return, unless your point of origin is also a pre-clearance airport. Delays going through immigration can be very long and it’s entirely possible that you may miss your connection as a result of this. IF you have a Canadian passport, some US points of entry (Toronto, Houston, Atlanta and probably others - I don’t have a complete list) have dedicated machines to read passports and automate the immigration process and you can use those to save a considerable amount of time.