Spiderman Homecoming HUGE Flop is MCU finished?

No not yet nor has it opened in Japan.

The Amazing Spider-man 2 made $125 million between those two countries. Homecoming could do more, could do less but it'll add a huge chunk to it.

It's probably got another $20 million or so left in US. Another chunk in the current overseas markets.

So it'll clear $800 million no problem. It's probably gonna make a comparable amount to Guardians 2.