Does ocean freight guarantee transit time?

Even though, most of the time, international sea freight shipments depart from the USA and arrive at destinations as scheduled, ocean freight cannot guarantee transit time.

Severe weather conditions are not the only factor that may impact transit time. Missing cargo delivery or shipping document cutoffs may result in cargo rollover to the next available vessel.  Roads and railroads traffic jams and misrouting may delay cargo arrival at a seaport. Vessel delays, junctions at cargo hubs during transshipping, and many other factors can result in delays in arriving shipping from the USA goods to the final destinations.

Typically, in events of delays, ocean freight carriers keep shippers informed. Even if a delay happens, most of the time, the routine delays do not significantly change the initially estimated transit time. 

We should note separately the possibility of delays related to cargo quarantine by the United States Customs and Border Patrol. Unlike routing delays, such delays are extremely rare. However, if the U.S. CBP flagged a container for the examination, then the delay may take uncertain time. Unless released by the U.S. CBP, cargo cannot be loaded on a vessel. Furthermore, additional charges due to the exam may occur. The charges should be equally divided among all owners of the cargo in the checked container. No one can help you with that. All complaints should be directed to the U.S. Customs and Border Patrol.