I applied to tenure track positions in the US when should I hear about interviews?
This will vary widely depending on the institutions. Since most new positions will only start around August there is plenty of time to have committees do some initial sifting of candidates. It might take a few weeks to a few months, actually. It is somewhat dependent on how needy they are to fill a position. If they feel at risk of not filling the position in the initial search they will want to save a bit of time for a follow up. 

Some institutions will be willing to give you some guidance if you ask and there is probably no real down-side to asking. Some will even list their deadline for decision in the application materials and will need several weeks prior to that to schedule any interviews. 

However, if you are a serious candidate, then you will likely hear sooner rather than later after the initial selection is done. 

Sorry not to be very definite, but every institution in the US is different in this regard and operates under its own rules and schedules.