Lots of contracts with a sufficient link to the US allow access to US courts, even with a foreign plaintiff. This is especially true for state courts, but sometimes federal courts are available too.
Suing a defendant based in the US for a breach of contract resulting from acts committed in the US, for a contract that doesn’t force arbitration or specify a foreign venue for litigation, would very likely allow a US lawsuit.
Naturally I haven’t looked at the specifics of the situation beyond what the linked article states, so this wouldn’t be legal advice even if I were a lawyer, which I’m not. I presume all the vendors whom the article says are contemplating a class action lawsuit are already getting proper legal advice from their lawyers.
Problem is majority of affected vendors are small fish, with reported (on kvr forum, LinkedIn, etc) losses of 20-30k. Individually, that's not enough to launch any kind of legal response, especially in a foreign country. Even more if there's a little chance of collecting anything from a (future) bankrupt entity.
Someone mentioned on that forum that Germany doesn't have class action suits, and majority of us were working with DigitalRiver Gmbh, because we started with German based ShareIt once upon a time.
There's a public 51 page document signed between Digital River and its subsidiaries and Cerberus Business Finance Agency, NY on 19 July, but it's too hard for layman to comprehend anything apart from that Cerberus is a creditor to Digital River and that it gets some extra rights from that point on. I'm just speculating since I'm out of my league here, but it's not impossible that they're using funds of small vendors who can't defend themselves to cover debt to a single large creditor armed with full legal team. If they drain all the funds and bankrupt the company, who can we realistically sue and expect to see some money? It's all legal, they were paying other creditor, money was not stolen for personal benefit.
