Just a few short years ago, each card was amazing, & that is what placed me on the path to wanting them all. But now, the focus seems to have narrowed to mostly just girls from eastern europe, instead of the worldwide options that used to be offered. Within the last 1-2 years the standard has become more like this:
I thought I would do some simple checking on this - it turns out to be sort of true, but also sort of not true. I just looked at the basic iStripper cards, not the iStripperXXX cards - .e. just the A and E series - and used their card ids to put them in order of production. This may not be a 100% acurate way to put them in order, but it should be close. Note that this ordering is not that of the release dates but of production.
0001-0500 - 11 countries - Australia, Austria, Belarus, Belgium, Brazil, Cambodia, Canada, China, Colombia, Cuba, Czech Republic
0501-1000 - 1 country - Czech Republic
1001-1500 - 5 countries - Czech Republic, Estonia, France, Germany, Hungary
1501-2000 - 12 countries - Hungary, Italy, Japan, Latvia, Mauritius, Morocco, Netherlands, Philippines, Poland, Portugal, Romania, Russia
2001-2500 - 11 countries - Russia. Serbia, Slovakia, Slovenia, South Africa, Spain, Sweden, Switzerland, Taiwan, Tunisia, Ukraine
2501-3000 - 3 countries - Ukraine, United Kingdom, United States
Final 30 cards - 3 countries - United States, Uraguay, Venezuela
While it is true that there have been two periods in which one ex-Eastern block country dominated - the biggest of these was not at all recent it was the period when almost everyone was from the Czech Republic and there has been a more recent shorter, and less overwhelming, period of dominance by girls from the Ukraine - but even in that period there were more cards in total featuring performers from the US and UK - though not by much.
I would describe this distribution as generally diverse, but with two streaks in which one country dominated.
Because I was not looking at the iStripperXXX cards they may reveal a different pattern, but I doubt it.