I do not know in particular about USAID, though I have tracked down examples of false claim that organizations did not use DDT. It appears likely that they did use it.
I see no evidence of large-scale efforts by environmentalists to reduce usage of DDT outside of the west. I have not examined claims like the one you quoted above that environmentalists in the US affected Mexico and thus Belize, but it doesn’t seem very plausible since it is easy to get Mexican DDT in America today
I do not know in particular about USAID, though I have tracked down examples of false claim that organizations did not use DDT. It appears likely that they did use it.
I see no evidence of large-scale efforts by environmentalists to reduce usage of DDT outside of the west. I have not examined claims like the one you quoted above that environmentalists in the US affected Mexico and thus Belize, but it doesn’t seem very plausible since it is easy to get Mexican DDT in America today