In a practical circuit and using a small-signal analysis, you can't.
You check the intented, purposely designed major loops with a small-signal analysis, followed by a large-signal transient (or pss).
The definition of single-loop feedback systems begs the question whether or not all possible loops in a multiple-loop feedback circuit should be checked (using multiple-loop feedback theory, simulated with nested 2GFT). Clearly, this is not possible as almost any practical circuit is a multiple-loop feedback circuit. Local feedback around transistors is abundant: source/emitter resistances (intentional or not), gate-drain capacitances... As a practical guideline, the intended major loops of a circuit should be checked. This implies that the designer assumes that the circuit that remains when those major loops vanish (loop gain zero), is stable. Any other loops will be taken into account during a transient analysis (or periodic steady-state analysis). A transient analysis should be performed anyway as it captures large-signal behavior.