QDM:
Hi, the reason we can still carry external loads on floatplanes is because it poses no great risk, I can only think of one fatal accident where the carrying of a canoe on a 185 with three passengers, full fuel and baggage resulted in the airplane stalling in a turn and augerring in.
It is noteworthy that he got it flying and high enough to spin in.
But that was unusual and of course you will always have pilots who push the envelope and crash.
Anyhow it is quite normal to carry external loads on floatplanes.
And I actually live in Canada, not the U.S.A. however there really is not that much difference in aviation between the two countries.
Cheers:
Cat Driver