If Indian courts aren't able to seize assets/impose judgements inside their jurisdiction, then yeah customers wouldn't have much recourse, I'm not sure what recourse customers generally have in that case then.
Jurisdiction is about whether the court is allowed to hear the case to begin with.
Enforceability of the judgement is about whether anyone has the power to do anything in practice if the defendant decides to ignore a judgement against them.
Just because the judgement you won turns out to be unenforceable in practice didn't mean the court lacked jurisdiction to hear the case to begin with. Jurisdiction and enforceability are separate concepts. Sometimes, the answer to the question of enforceability does not become clear until long after the judgement itself.
US courts (both federal and state) have the power to enforce foreign court judgements; I'm not aware of any rule which automatically excludes Indian courts from that. Whether they will do so in any particular case is a very complex legal question. In theory, the question of whether a US court will enforce a foreign judgement is based on legal considerations not political ones. Of course, in practice, judges are political animals and they will take political considerations into account; but, when they do that, they generally try to explain what they are doing as applications of apolitical legal principles, no judge wants to be openly seen to be deciding a case politically even if many suspect that to be their true motivation.