Ricardo's comparative advantage result is contingent on the assumption that capital is not mobile across borders. This was a good assumption in 1817. Is it a good assumption today?

Furthermore, he's very up front about this in On the Principles, and from this information you can calculate the exact number of people who read the damn thing between the person repeating the talking point and the person originating the talking point.

In 1817, capital did not cross borders. Borders crossed capital.

I don't know it makes much difference. People could walk from country to country in Europe back then and still can, likewise you could move money and equipment and still can.