Can I communicate with multiple USB RSAs Simultaneously?

Yes there are two options to communicate with multiple RSA's:

Two USB RSA's can be controlled through the software DataVu-PC. DataVu-PC offers recording using two RSAs so that you can operate at two independent frequencies and spans simultaneously. One instrument can be used for wide-span signal detection and a second instrument can be used for isolation on signals of interest and recording for later analysis. Or, both instruments can be used for recording. You can record in bandwidths from 9.7 kHz to 40 MHz. Recording in narrower bandwidths reduces data loads, minimizing disk space and search times. You can also use DataVu-PC to show DPX displays for two RSA's at the same time. Further DataVu-PC software information can be found here: https://www.tek.com/datasheet/datavu-pc

The other method is by using the RSA API. In order to communicate with multiple RSA’s simultaneously you will need to call multiple instances of the RSA API. The API will need to be called for each RSA. 

RSA API GitHub: https://github.com/tektronix/RSA_API