Sperms of the world

Thinking further about that vat of USA Sperm.
It's striking that of all the sperm in the world, we use USA sperm. I presume this a simple logistical issue. But as a post-Colonial society, why not British sperm? Or (gasp) Indian or Chinese sperm? I won't go Aboriginal sperm as I can't even joke about it without bringing stolen-generation spectres to mind.

I'm assigning national characteristics as I type - USA sperm: fat and arrogant but energetic, so will probably do the job. British sperm, well-dressed, a bit restrained, might be a bit slow to get moving. Intelligent Indian sperm. Maltese sperm would be far too laid back, it would never get to the point, sitting down and having a coffee with every other spermatazoa it passed along the way. 'There's no hurry, here, have a pastizzi.'

(Are assumptions about national characteristics racist? Or are we meant to assume that every race has the same intrinsic characteristics? Bearing in mind I think these characteristics are cultural not hereditary. So many shoulds).