But that’s exactly how I would say it: “millions of dollars was at stake.” To me, what you propose seems like a mistake someone just learning English would make.
Give it a specific sum: you wouldn’t say “two million dollars were at stake,” you would say “two million dollars was at stake”. I admit it’s pretty weird, but you also say “two million dollars is a lot of money,” not “two million dollars are a lot of money.”
IIRC this may be a difference between British English and American English... Whereas a Briton might say “Led Zeppelin were on stage”, referring to the multiple band members, an American would say “Led Zeppelin was on stage”, referring to the band as the single entity. I can’t remember where I read about this though.
You’re correct! They take it pretty far: for instance companies are collective nouns, so they would say “Apple are releasing the new iPhone.” In not sure where it stops, but I’m vaguely suspicious that countries are singular nouns.
Give it a specific sum: you wouldn’t say “two million dollars were at stake,” you would say “two million dollars was at stake”. I admit it’s pretty weird, but you also say “two million dollars is a lot of money,” not “two million dollars are a lot of money.”