I have been playing this game for a while now and its really entertaining.
I live in Europe and have two accounts on PSN. One US and one European and the main reason for this is that in the beginning I had a problem that games used my native language instead of English and in some cases you can buy some games a few days, weeks earlier. When bought at US store that problem was solved. Today this is fixed in many games also in Resogun, so I mostly use the PSN-account for Europe-region.
Now to the point.
Resogun, bought at US store, played with EU account works fine, but friends cannot compare my challenges, feats etc, neither can I with theirs. So I though i re-buy the game in EU. Now, all my progress is gone, nothing unlocked BUT highscores from US version works, but challenges, feats, story mode locked even if I can see my US scores on that challenge etc. If I start US version everything back to normal.
So, if you go to your friend which uses US account since its his native language and you play there you have to restart everything. We tried his account on my EU-game, he is also back to zero there so it has to do something with playing with US/Europe with correct PSN-account to that region.
Should it behave like this, its kinda sad
. I compared the games and the US use parental level 4 and EU level 3 so there might be differences in the game itself.