I do not know who needs to know this but if you hold an American Express credit card abroad that earns membership rewards points, it is possible once a year to transfer points between the two accounts. This can be particularly useful if the transfer partners are more favourable in one country or another and/or the exchange rate is favourable.
For instance, I hold a German AmEx Blue card and a Canadian AmEx Green card both of which earn membership rewards points. I can transfer my German AmEx points over to my Canadian account at a rate of the Euro to CAD exchange rate (current 1.62 CAD per EUR). This is appealing since AmEx Germany has a transfer rate of 5 membership rewards per 4 British Airways Avios points. Over in Canada, it's a simple 1 to 1 rate. To give you a concrete example of this advantage, suppose I have 5,000 AmEx membership rewards points in Germany. I could convert those 5,000 points over to British Airways and receive 4,000 Avios points. However, if I were to transfer the 5,000 points over to Canada, that would become 8,100 membership rewards points which in turn can be converted to 8100 Avios points. I don't know about you folks but I'd take the 8,100 Avios points over the 5,000 Avios points all things being equal.
Now of course this supposes that you hold an overseas AmEx credit card that earns Membership Rewards points. In my case I was lucky having grown up most of my life in Canada, I hold several cards one of which is the no annual fee AmEx Green card. But it's something to keep in mind if you have the option as it effectively makes these devaluations irrelevant.
For those curious, here's a guide that explains the process for a transfer between Canadian and American AmEx products:
How to Transfer Amex MR Points Between US and Canada | Prince of Travel
-RooFlyer88