Just say "Trump was right". You will not be condemned by bien-pensants as a thought-criminal. At least, not immediately.
>I just wish he could get the USPS to stop seeing outbound international mail as a profit centre.
In other words, you'd like to pay less when buying from the US.
(There's nothing wrong with such a wish, but let's be clear about what you mean.)
>Plenty of Americans could be exporting a lot more internationally, but the USPS has chosen high prices and low volumes.
I know of no evidence that the USPS charges more to ship internationally than Canada Post, notorious among Canadians for high prices. On the contrary, it's sometimes cheaper for Canadians to ship to elsewhere in Canada by mailing from the US. (Discussion: https://www.reddit.com/r/canada/comments/6rcn0v/canada_post_... )
>As a Canadian that sometimes talks Americans into selling to me on Ebay, they find it a painful and costly experience compared to US sales.
That's because it is, compared to mailing domestically. It'd be surprising otherwise, for any country.
I've sold on eBay and Amazon for years and have shipped often to Canada and elsewhere; the procedure isn't that much more cumbersome. The vast, vast, vast majority of sales are within the US, however.
It's quite possible for an American seller (whether on eBay or Amazon or with their own online sites) to make money solely from the US market. Canada is one ninth of the US and a smaller portion of potential sales for American sellers. A Canadian seller, on the other hand, knows that the American market is nine times larger than the domestic one, so has much more incentive to a) learn how to handle international orders, and b) be willing to pay the higher postage rates.