shame we didn't know the answer to the above
https://www.thefa.com/football-rules-governance/policies/player-registration/points-based-systemFeel free to peruse at your leisure. I'll try to find the relevant bits and update this post once I do
Edit:
16. An Assistant Manager will only be granted a GBE if:
a) The Assistant Manager will have Partial Responsibility for the first team of the
applicant club.
b) The Assistant Manager holds a UEFA ‘A’ licence/diploma or equivalent.
c) The Assistant Manager has:
i. Managed a club in a Top League for the Prescribed Time; or
ii. Managed an international team for the Prescribed Time which had an
Aggregated FIFA World Ranking of 50 or above for the entire Prescribed
Time.
A Top League is any league in Bands 1-5, of which the Swiss League and MLS are, so that's fine. The Reference Period is either 36 months within the last 5 years or 24 consecutive months in the last five years