Just take a naive sample, all US president after WWII. Finding all 国务卿,总统子女 sounds too much and I will skip that and leave it to someone else.
All of them are with US educational background only.
P.S. to give a statement, you need some reference. for example, if i have to show your statement, i will try to list out all the children of 国务卿,总统 of US, and see the proportion that they study in US, UK, elsewhere.
state an argument without any support, is simply bull shit, unless that's a really common sense that every one agree.