Actually USB3 and Thunderbolt are very similar... Thunderbolt is small-cable version of PCI-Express :
Thunderbolt controllers multiplex one or more individual data lanes from connected PCIe and DisplayPort devices for transmission via one duplex Thunderbolt lane
Wikipediaand USB3 is also somewhat of a copy of PCI-Express :
5 Gbit/s (electrically it is more similar to PCIe Gen2 and SATA than USB 2.0
WikipediaIt's not by chance that USB3 is 5GBit/sec, that's also the speed of a 1x PCI-E lane in Generation 2 mode (although that's actually GigaTransfers/sec). In addition USB3 supports multiple transfer modes, namely isochronous, interrupt, or bulk transfer. Both isochronous and interrupt modes can be used for streaming data (low latency).
And finally... no system actually streams data instantaneously... they all utilise buffers, interrupts, negotiation and timing synchronization, all of which impact the latency of data throughput. Processing of data, regardless of what bus/source it originates on entails an interrupt being called so that the CPU can start manipulating that data.