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While a ground is recommended for many reasons you don’t always need one to receive signals. For example you can use a dipole antenna and feed it into the RSP with a battery powered laptop and get great results. An automobile transceiver (CB or ham radio) does not have a connection to earth because it is on rubber tires and they work very well. The issue of grounding or not depends on your requirements for lightning protection, electrical safety and if you are using certain types of antennas like a vertical.
In your case you are feeding a long wire directly into the RSP input via one meter of coax. So what is the other half of the antenna? It is the shield on the 1 meter length of coax and the shield of the 32 feet of the active USB cable. This will be a very noisy arrangement and you will have a very poor impedance match to the input of your RSP. The end result is low signal levels with lots of local noise pickup from all the digital devices (washing machines, heat pumps, appliances) in the vicinity.
If you are into serious listening you will require a better antenna setup. End fed or random wire antennas can work well but you generally need an impedance transformer and some current baluns (RF chokes or line isolators) in order to get the noise floor down to an acceptable level. The subject of antennas is a broad topic and there are many resources and sites on the Internet devoted to short wave listening antennas.