You are correct, BUT.........................
FAA requires you to be in jump seat STRAPPED in during NON safety related duties while on the ground during taxi, take off and landing........ WELL
YOUR "Work and Conduct" rules state:
2-1 12. Violate an FAA RULE which results in your being permanently barred from performing your JOB as a FLIGHT ATTENDANT.
I would say that not being able to fit in a jumpseat stapped in violates an FAA rule.
So, yes, US does not have a weight requirement!!!!!
And before someone says "Well the jumpseats are not big enough"! Well, the FAA doesn't feel that way otherwise they would have made them bigger.
They are the size they are for a reason.