Look at the US and Mexico: Despite having a lot of trade and migration, the two countries significantly differ economically.
So it plainly does not hold that trade and migration entirely eliminates differences.
Brahmins in India had high social status but less money/assets in past. So I am not talking about economic status.
And indeed, Mexico is gaining ground on the US, not least because of bilateral trade and bilateral migration.
Back then labor was in more demand. Evidence is the salves were imported often at great cost and risk.
There were fewer commodities in market.
Germany had coal, French needed it.
There was no limit on immigration.
People from Germany and France were more equal in education and social status than the difference you've between Americans and Mexicans.
Technology wise countries in Europe were quite equal, what differed is the amount of resources at their disposal.
>So it plainly does not hold that trade and migration entirely eliminates differences.
It doesn't have to entirely eliminate differences, just have to make them more equal.
> People from Germany and France were more equal in education and social status than the difference you've between Americans and Mexicans.
Good way to disqualify any counter-examples to your theory. If they're more equal in status (i.e. have more equal economies), then they don't count.
This assumes that the colonialists countries didn't trade with non colonialist countries in Europe.
Prussia initiated the concept of a common market in 1818 and in 1833 a treaty extended the Zollverein to the larger states of Germany, although Austria, by Prussian design was excluded.
As demand for coal increased, Germany rapidly developed railway and coalfields
We see lots of migration between Europeans countries specially ones with linked borders. There is movement of goods and people which itself can pull multiple of European countries to higher wages levels and living standards.
If french were getting richer and Germans were extracting coal. Germans could sell their coal at much higher price to French and grow rich without getting into colonialism.
If you cross the border and make much higher wages, the news would spread and regions would equalise overtime unless there is something which artificially stops migration.
Here's the data (which confirms high migration rates): https://brewminate.com/internal-migration-in-france-and-germ...